Affordable and social housing finance innovation - synthesis, reflection and implications for Scotland: international evidence

Evidence Review

The findings in the central part of this paper are grouped into two main parts. First, we examine the central learning points from four national and international cognate studies between 2010 and 2019 that I co-authored or authored solely. The second strand looks at a small number of international evidence reviews relating to affordable supply and finance, again seeking to draw key messages, including across a series of discrete interventions around land, guarantees, private sector participation and other specific national instruments.

A. Glasgow Research

Hall and Gibb (2010) focused on social housing supply and its financing. It was written for a housing market taskforce undertaken by the Joseph Rowntree Foundation (JRF) in the immediate aftermath of the 2007-08 GFC. A brief review of international evidence (Whitehead and Scanlon, 2007) found evidence of discernible broad trends being played out across Europe:

• As mentioned earlier, a trend away from supply-side to income-related demand-side subsidies, from the use of subsidy to that of debt finance, and from subsidy to 3^rd party (planning gain) contributions such as developers, landowners, and from employers.
• Growing appetite for private equity created from various public-private partnership arrangements or direct purchase.
• Special housing finance circuits that combine public borrowing or subsidies, and in the case of Finland, Holland, France and Sweden, state backed or indeed mutual funds borrowing through loan guarantees (e.g. Gibb and O’Sullivan, 2009).
• Regarding equity finance, Whitehead and Scanlon note the recycling of assets through sales to sitting tenants, leveraging unencumbered assets (including land), the directed use of accumulated reserves and cross subsidy (affordable homes programme in England).
• A general search for alternatives to traditional public subsidy. One is land – either offered by public landowners at below market prices or through various forms of through contributions made by developers or landowners. Several countries continue to use cheap public sector land because it need not be identified in public accounts. This is also important in regeneration projects in countries like Holland, Denmark, France, Germany but was evidenced in England too.

Gibb, Maclennan and Stephens (2013) was also a JRF project examining good practice and innovation in affordable housing finance internationally, in what was then an increasingly challenging context for the supply of social and affordable housing. The report’s key messages (p.1) were:

• in a challenging fiscal context, innovation is needed to stretch limited public subsidy and increase private contributions to help deliver additional affordable housing.
• the evidence review indicates that to encourage new investment, supply is likely to be at the affordable rather than the social housing end of the spectrum. this is despite the pressures on Housing Benefit and high and increased levels of housing need
• While interesting ideas that are worth exploration and possible transfer are evident, financial measures such as those discussed here need to be understood in a wider policy context of housing system failure and the continuing need to support new housing for those on low incomes.

These three points have a resonance for today – the paradox of pursuing affordable rather than social housing even though need is apparently increasing^[7], and HB costs will be stretched by higher rents and less tenancy security. Second, we must always be wary of the contextual, institutional and path dependency pitfalls cross national policy transfer.

The authors also argue that there are ways forward we are likely to see (p.3): “on the one hand, there is a desire to use more state-backed guarantees, encourage competition among providers, sweat existing assets and encourage alternative sources of provider income. On the other hand, opportunities also exist to ‘blend’ different subsidies creatively and encourage solidarity-based co-operation among providers”. The authors, however, also argue that the evident longer term market failures in both credit and land markets, alongside inelastic supply and increasing income poverty requires social housing to be prioritised rather than affordable rents.

The research examined interesting and potentially valuable approaches to affordable housing finance and subsidy routes across the UK, in the Anglosphere and across Europe. Broad themes of continuing resonance included:

• Cautious enthusiasm for guarantees but concern about design and governance implications. Nonetheless, positive examples include Finland, the Netherlands, the National Housing Trust in Scotland model (counter-cyclical, additional, sensible exit routes)^[8].
• An interest in contestability – finding ways to compete or contest access to subsidy both for non-profit and for-profit providers linked to outcomes and performance (and perhaps funding routes such as social investment and social impact bonds).
• Lessons from federal political systems where subsidy is blended between higher level jurisdictions, applied to local levels where creative use of, for instance, land can help deliver targeted customised affordable solutions. Greater discretion with in regulated systems focused on VFM could provide for more flexibility and greater experimentation on a bottom-up basis augmented by national government supports. The case can still be made for assisting here by revising UK accounting rules over borrowing to bring them closer to European norms (Lloyd and Grayston, 2023).
• While there is much interest internationally among policymakers in complicated schemes such as affordable REITs, sale and leaseback models and tax credits – there is much to be said for simple transparent and accountable programmes.
• Affordable rents imply a thinner programme where shallow subsidy can be spread further and as the Affordable Homes programme illustrated – this can be combined with sweating equity by in that case reverting vacant social tenancies into affordable ones to cross subsidise lower grant contributions. These are challenging trade-offs.

The authors also identify specific models that have a wider currency for possible application and customisation in a UK context. Two examples not mentioned already are, first, the Irish model that developed private tenanted stock being given long leases so that the properties could be let to low-income tenants and where the public provider would take the risk of voids in return for a discounted rent. More recently, the Irish government has also piloted Austrian cost rental in Dublin – a model we discuss further below in the box^[9]. Second, as we also discuss below, the Danish housing association national surplus fund is a collaborative, solidarity-based revolving model which can reinvest rental surpluses for different national housing policy objectives.

Inset 1: Austrian Limited Profit Cost Rental Model

‘Austrian limited profit housing comprises mainly medium density multi-family apartments, managed on the basis of a cost rent, limited profit business model and are financed in part by conditional public loans, tenant and association equity and private loans (often financed by (until recently) tax privileged housing bonds). [There are around 900,000 limited profit cost rent housing in Austria – about 17% of all housing]. Associations operate under Limited Profit Legislation and Rent Laws and are generally financially stable, well-regulated providers. Limited profit housing providers tend to be the primary deliverers of subsidised housing. They also play a trendsetting role in real estate development and planning standards, promoting innovations in socially and environmentally progressive standards, designs, materials and construction and in some cases social inclusion’ (Gibb and Hayton, 2017, p.37).

The key principles of limited profit cost renting in Austria (selected from Lawson, et al, 2021, table 7) involve (1) cost rent based on debt servicing, management and maintenance; debt free homes operate with rent control; (2) limitation of profit clearly specified legal limits on surpluses; (3) revolving funds – surpluses are continuously reinvested and equity in the business is strictly controlled; (4) independence from the construction sector (5) limited diversification form core business, and (6) independent auditing/regulation.

In Vienna, the limited profit model has been supplemented by, the ‘Wohnbauinitiative’ (Housing Construction Initiative), which encourages multi-apartment housing construction and addresses unmet housing need in Vienna (van Bortel et al, 2019)..

Other Sources/further reading: Amann et al 2009); Deutsch and Lawson (2012); Lawson et al (2021)

Pump primed or organic revolving funds (in this case, generated by retaining the same level of rent after debt is paid off and recycling the accrued surpluses in a national fund) can be large or small but in both cases make a real difference. The Netherlands have developed a mutual assurance system where associations pay in and build a fund to protect each of the members financially as a form of insurance; the Scottish Highlands have operated revolving land funds; and, English Partnerships used pump priming to help then initially fund land development and infrastructure elements (site and services) before selling the serviced land on to developers and social providers, reinvesting the income they made to carry on future land purchases.

Gibb (2018) is a position paper on affordable finance and subsidy, part of a working group considering the future of social housing in England. Three sets of ways forward were articulated to support and extend social housing:

1. Land has several market failures (Gibb and Hayton, 2017; Gibb, 2019). Overcoming land barriers: pricing public land for sale; land value capture; land value taxation; regional and national development agencies; the role of CLTs

2. Financing innovations: local housing companies (in the absence of public accounting change); affordable REITs; new aggregators and state owned or backed investment banks

3. Subsidy: redesigning personal subsidy (better recognising the trade-off between shallower subsidy, higher rents and the benefit bill/or in work poverty; revolving funds; revenue subsidy including guarantees or state-backed contingencies or outcome-based social impact bonds and other forms of social investment

Gibb (2018) concluded with support for blended subsidy systems, intelligent use of guarantees, land value capture mechanisms, and agreed that it was also worth looking also at revenue instruments such as profit-sharing and ground rents to equity partners providing land or infrastructure.

Gibb (2019) is a chapter on financing housing within Shaping Housing Futures (Maclennan et al, 2019), a tri-country study of housing strategy and policy in Australian, Britian and Canada.

In this paper, possible ways forward to fund affordable supply were identified across the three nations studied:

• Does the sector need to restructure or (at least) consolidate the developing not for profit sector?
• Sweated equity e.g. stock transfer and using unencumbered stock as security for loans though this skews development to bigger operators
• In the UK, remove HRA borrowing from public sector borrowing
• Introduce national or regional land delivery vehicles (revolving fund funding)
• Fiscal incentives to encourage re-use of empty homes
• Compulsory sales orders applied
• Applying ‘soft’ repayable loan (e.g. financial transactions capital) and equity stakes from government to pump prime affordable investment (i.e. grant-free mid-market rent in Scotland)
• Guarantee rental payments initially in new developments (as was proposed with BTR in Scotland).

In conclusion, Gibb (2019) argued that housing systems were experiencing less of a crisis, more a set of overlapping chronic problems: path dependency operating in a complex system, the importance of unaffordability and lack of choice. Moreover, there was no silver bullet financing solution; but rather smart ways required to use for example private equity in a social housing context. Fundamentally, governments also need to follow Ballantyne and must make the best case for bigger smarter programmes: prevention: building that argument around the costs of inequality; macroeconomic benefits; cost benefit analysis and preventative benefits/budget savings^[10], and better framing and communications.

Key messages:

• A complex system and, post GFC, a changed world trending away from the traditional model for social housing and not re-establishing a new model thereafter other than searching for other ways to fund affordable (less now traditional social housing).
• Is the shift towards affordable supply appropriate given the mounting evidence of unmet housing need and unaffordability?
• Blended subsidies in multi-level governance systems of considerable interest – but works better in federal systems with more well-established fiscal federalist systems of inter grant transfer, etc.
• Guarantees and low-cost debt have a long lineage with good practice versions in countries like Finland (see below), as well as earlier examples e.g. National Housing Trust in Scotland, as well as soft loans such as those associated with Financial Transactions Capital.
• Solidarity based approaches such as the Netherlands, and particularly Denmark (the latter is well received, much like the national wealth funds in countries like Norway) but it must be bult up and there needs to be a ready mechanism of building surpluses and a sector acceptability to use these in a directed top-down way.
• The importance of overcoming land barriers: discounting best value sale prices for public sector land to social housing providers, exploring land value uplift measures to help fund development related infrastructure, the use of both local and national revolving funds, tax reform e.g. council tax on land with planning permission, CPO/CSOs, development agencies and revolving funds.

B. International Evidence Reviews

Here we look at cross national studies, including a book by van Bortel and colleagues (2019), a highly useful UN/ECE study (Lawson, et al, 2021) and we provide an overview of several relevant Australian AHURI reports and the themes that flow from them.

Del Pero, et al (2016) provides an OECD-wide examination of the need for affordable housing and a sense of the different high-level approaches open to national governments. This is a good high-level analysis with which to diagnose unaffordability and to consider how different national contexts among OECD members impact on the interventions pursued, but we need more analytical evidence of those interventions to proceed further. The van Bortel et al volume focuses on national case studies of both governance collaboration and financial partnership between the state, market and community. Alongside a growing role for the market sector, the state is still seen to need to play a role involving regulation, guarantees, incentives and subsidies – to make partnership finance for housing work. The authors summarise finance for affordable housing in NW Europe thus (p.6):

“Social housing is traditionally financed by mixing various resources. Most dominant combinations in North-Western Europe are:

• state guarantees, grants and/or loans combined with bank loans, attracted by the social housing provider and paid from rental income, in the case of social rent (public or third sector);
• state grants and institutional investments, in the case of market actors providing social housing;
• state grants combined with mortgages, attracted by the household, in the case of home-ownership;
• state grants combined with cooperative funding mechanisms, in which households buy shares in a cooperative (funded by specific mortgage schemes and/or own resources) and/or paying a rent to the cooperative;
• bond finance (corporate bonds; national, regional or local bonds).”

Regarding affordable housing supply innovation, the UN/ECE research ‘Housing2030’ by Julie Lawson and colleagues is a broad based and comprehensive tool box of strategies, policies and analysis open to governments wishing to develop a more coherent mixed tenure housing system that is affordable and high quality. For our purposes it is valuable because it both draws analytically on general approaches to e.g. financing affordable housing but also digs deep into country case study good practice e.g. the insert examples used here of Austria, Finland and Denmark^[11]. Housing2030 establishes a number of important principles of tools for successful affordable housing finance supply systems (Table 9, pp.52-53). These are a useful checklist to consider when looking at specific proposals in certain places or jurisdictions^[12]:

1. Regulating financial institutions and housing institutions within that wider frame, thereby creating a stable and predictable framework, robust social housing regulation, but also a less volatile housing system and credit market.

2. Non-profit provision characterised by reinvestment of surpluses. This can also be applied to reducing long term cost rents or growing revolving funds for use in social housing.

3. Rent subsidies – government assistance to meet housing costs though design and interaction with choices and other economic decisions is critical and (highly variable).

4. Rent setting, indexation and regulation. The process of setting and then raising rents varies by tenure and may also various across groups of tenants and places.

5. Microfinance – non mortgage backed and can help occupiers make small investments in their homes often on the borders of formal and informal housing.

6. Circuits of household savings schemes – several examples where the flow of such savings in dedicated state schemes, are a vital source of funds for affordable housing e.g. France. Generous savings returns provide resources for social housing and to aspirant owner-occupiers (with lending rates a little higher than savings rates), as well as a form of solidarity that helps build stability and resilience.

7. Public loans, grants and public investment in housing – important support e.g. grants reduce requirements for further borrowing, access to state loans spread costs and may be more favourable than equivalent market terms; such interventions may also help pursue wider social, economic and spatial policies.

8. Interest rate subsidies, guarantees and insurance. Reducing debt costs by insuring or guaranteeing mortgages can protect lenders and hence reduce interest required.

9. Special purpose financial intermediaries channel funds form state, market and the personal sector to affordable housing provision – they can operate across a mixed economy spectrum and can be just as effective as a not for profit as private sector or indeed a state entity.

10. Sharing housing equity and costs can be particularly relevant to the marginal home ownership sector and may also extend equity shares and deferred payments to other areas such as potentially retrofit.

11. Revolving funds which repeatedly reinvest in housing. These are closed or ring-fenced circuits of housing investment that recycle loans, rent surpluses, land funds etc into new investment. They can operate at the local or national scale and often use initial pump-priming funding to get started.

12. Taxation to guide investment in housing incentivising provision, consumption, occupation, mobility, investment and maintenance, as well as, for instance, encouraging the use of land or bringing empty homes back into use or discouraging specific uses.

Below Insets 2-5 draw on the ‘Housing2030’ evidence to look more closely at, respectively, models in Finland, Denmark, generic land market interventions and savings instruments to fund housing in France.

Inset 2 Finland and financing its affordable housing

Finland has a long-established, well-regarded model for funding social and affordable housing. It is centred around their national Housing Finance and Development centre (ARA) – an agency of government. Non-profits seek funding from ARA for social housing construction and renovation and ARA also provides financial support to home ownership. do social and affordable renting, ARA uses a mix of grants, subsidies and guarantees. Lawson et al (2021, p.80) note:

“Critically, ARA loan guarantees and other supports are only made available following detailed assessment of the financial sustainability of housing projects and sponsoring organizations. Furthermore, certificates are only provided for loans with the most competitive terms, driving down the costs further. ARA also controls and monitors use of the housing stock it has funded and monitors and directs non-profit housing corporations to ensure good financial management and appropriate use of government subsidies’.

‘Since the global financial crisis, ARA guarantees have been extensively used to source low-cost private-loan finance via the special purpose financial intermediary called Munifin, which is owned by the Finnish municipalities. This arrangement has reduced the cost of financing and hence the cost of interest subsidies considerably”.

Source: Lawson, et al, 2021; also see Lawson, 2013.

Inset 3 Denmark: Landsbyggefonden (National fund for non-profit housing associations)

Denmark has 600,000 social housing units – housing more than 15% of all households. Its national building fund established in 1967 and financed from tenant rent surpluses is a central part of what is a durable and resilient system. Lawson, et al (p.62) argue that: “When mortgage loans for dwelling construction have been repaid, tenants pay rents at the same level, with the extra going into the LBF as a saving. This fund finances the expansion of new affordable and social housing and renovation of existing properties. This includes improvements of both inside and outdoor areas, modernization of buildings to include access for elderly and disabled people, and energy improvements. The fund is also able to finance the demolition cost in vulnerable social housing areas, and to support infrastructural changes”. They go on:

[The LBF is] “a useful mechanism to ensure self-financing in the social and affordable housing sector. Savings are recycled to help maintain and improve dwellings and provide additional housing. It thereby provides a sealed finance circuit, reducing government need to reinvest in new social housing, and facilitates long-term planning for social housing funding. It also helps to even out variations in the financial strength of different social housing providers, in the costs of developing different estates, and thereby in rents charged which reflect development costs”.

Its advantages are the long-standing nature of the fund, one where HA maturity and debt repayment brings forth more surpluses for reinvestment and the model grows over time not unlike a sovereign wealth fund. It is stabilising and indicates the benefits of long-term policy continuity. Its governance is vital however because it is a national funder and needs to retain the buy-in of housing associations. Clearly such a model could work at more specialised or regional levels too.

Source: Lawson, et al, 2021

Inset 4 Land interventions to overcome land market failures

Looking at the elements that determine the efficacy of social and affordable housing supply, both a reason for needing affordable housing and a barrier to it- emanates from failures in the land market. Developing a battery of policy levers and good practice intervention mechanisms in the land market can make considerable difference. In Scotland the run-up to NPF4 included considerable debate and consultation over land market reform, not least via the Scottish Land Commission. These issues are somewhat stalled but there are unsurprisingly important lessons internationally that can contribute to helping relax what are often critical constraints to development.

Lawson et al (2021, chapter 3) identify several key barriers and corresponding policy instruments. These include: (1) Public land banking – where government develop a portfolio of land for housing and larger development opportunities through open market purchases, compulsion (purchase or sale) where required and in the public interest, and through unlocking public land as well. This also raises the question of reducing the cost of land sold between public sector bodies or where it is for social housing and not requiring best value commercial maximisation of the receipt. (2) public land leasing – which can reduce upfront project costs and improve affordability. (3) Land readjustment – a process of consolidation and land assembly wherein reduced purchase costs can be traded off for equity shares in the development; (4) land value capture instruments – familiar to the UK but important ways to pay for infrastructure and to make land more affordable in the first place e.g. through social housing use classes and removing or mitigating hope value; (5) taxation instruments such as creative use of local and transaction taxes to incentivise development of sites with planning permission, bring back empty homes into use, and adopting land value taxation principles.

Source: Lawson et la, 2021; see, also Macfarlane, 2017; Crook, 2018, Aubrey, 2018a & 2018b; Bentley 2018 &, 2018b, Jones et al, 2018

Inset 5 France savings funding mechanism for affordable and social housing

Since 1816, the French have mobilised government-backed personal savings accounts (Livret A) through a national scheme, the CDC (Caisse des Dépôts et Consignations). This long-lived scheme (starting in the first half of the 19^th century) is a key, at scale, contributor to the funding of social and affordable housing (and home ownership). Currently there are circa 50 million Livret A accounts, which in 2020 held more than 400 billion euros in savings. According to Lawson, et al, 2021 (p.73):

“Livret A savings accounts are available in all French banks; they are popular because they offer an attractive interest rate, tax-free, and state guaranteed.”

“Some 65 per cent of deposits from Livret A savings accounts are centralized in CDC and used to fund social housing construction and refurbishment loans. These loans are provided at slightly above cost, that is, above the Livret A interest rate, the average of the previous year’s consumer price index (CPI) inflation and the Euribor & Eonia... The result is that interest rates are generally below those available from commercial lenders. Critically CDC social housing loans are also provided for long durations, which helps spread the costs of social housing provision over time. Loans for social housing refurbishment and modernization are available for 15-30 years, loans for social housing construction available for 40 years, and for 50 years in 20 per cent of cases.”

“CDC provided around EUR 10 billion in new financing for development or acquisition of new social housing units in 2019, which helped add 78,740 dwellings to the French social stock. It also provided EUR 1.9 billion to help finance renovation of social housing units. For 2020-2022, the objective of CDC is to finance the delivery of 110,000 new social housing units per year plus renovation of a further 125,000 social dwellings”.

Source: Lawson, et al, 2021.

Key Messages & Implications

• Many of the success stories across Europe – Finland, France, Denmark, Austria – represent long term stable and predictable successful policies which both help moderate the pro-cyclical nature of housing, insulate social housing from the market, also building up and maintain revolving funds and similar special circuits. These draw strength from the maturity of their sectors. They also indicate that moving to this path and away from ‘business as usual is unavoidably a long-term proposition, but that does not mean one should avoid starting down such a road. Land reform is important but takes time but that is no reason not to proceed.
• We should recognise the importance and complementarity of green retrofit to housing cost and wider household affordability, and that finding efficient and incentive-compatible mechanism to co-fund the capital cost and running costs of retrofit is essential to sustain investment in new social and affordable housing. Finding a solution to retrofit and investment will lighten the load on providers and in turn support making housing more affordable and reduce energy costs for those on lower incomes. This should be seen as a joint and complementary endeavour not an either/or option. Work is urgently needed to come up with smart ideas and learn from the ideas found internationally such as those above in Germany and the Netherlands. Note that in Scotland under EESSH1, social housing providers made great strides to achieve targets making the tenure the most energy efficient part of the housing system but more than 85% of these investments were paid for by tenants through higher rents^[13].
• Path dependency is important e.g. the strength of the social housing responses in countries like Austria and Finland do not operate in a vacuum and are supported by a network of interlocking finance, regulation and strategic mechanisms, as well as long established partnerships, trust and verification. It is not straightforward to graft these models on to Scotland. This is one further reason why it will be immensely valuable to see how the Irish experiment with low cost for limited profitability rented housing works out in the coming years (as it will with their different evolving long term leasing policies)^[14].
• Housing2030 establishes that developing resilient housing finance circuits specifically for affordable/social housing delivery can create durable and stable models that allow for implementation but also considerable forward planning.
• Housing2030 indicates that there are long established financial circuits supporting housing through state savings schemes in France, as well as interventions to encourage investment in retrofit that need not undermine new affordable /social housing supply in countries like the Netherlands and Germany.
• Housing2030 also sets out a series of ways to overcome land barriers through diverse interventions like public land banking, land readjustment and taxation, as well as through measures we are more familiar within the UK concerning land value capture for social good.

Australian Housing Research

Since the 2000s, much of the best policy-oriented housing research has emerged from Australia through their Australian Housing and Urban Research Institute (AHURI). They have promoted housing-related comparative studies and international evidence reviews, many of which consider finance and subsidy innovation for affordable housing. Here we have reviewed relevant evidence from eight studies written between 2004 and 2018 (Berry et al (2004); Milligan et al (2009); Pawson, H, Lawson, J and Milligan, V (2011); Lawson, J. (2013; Lawson, J Berry, M, H Pawson (2015); Milligan, V, Pawson, H, Williams, P and Yates, J (2015); Newell, G., Lee, C. and Kupke, V. (2015); Rowley et al (2016); and, Randolph, et al (2018). We have drawn on this body of research throughout the paper but here just focus on two pieces of work on guarantees and REITs.

Guarantees (Lawson, 2013; Lawson, et al, 2015, see also Gibb and O’Sullivan, 2009). Lawson (p.2) argues that the expanded use of guarantees for affordable housing is a balanced one and they need to be well defined and clearly address their objective. “Guarantees are used by many governments to reduce reliance on public funds, build market confidence amongst new investor segments and accelerate investment in required social and economic infrastructure such as social housing. They aim to bolster the credibility of new initiatives and can be used to establish new pathways of investment. Ultimately, they aim to attract suitable long-term investment and reduce the cost of finance…. Arguments against the use of guarantees include the moral hazard of supporting risky but desired investments. Also, the difficulty in measuring the effect of a guarantee on loan interest and terms has been raised. Further, the danger of oversupplying investment to a particular market and creating unfair competition with other forms of investment has led to the refinement of some schemes. Some opponents argue that guarantees can promote inefficient practices as recipients receive lower cost credit without ‘market discipline’.”

Residential REITs. In a review of residential REITs internationally, Newell, et al, 2015, p.16) identified two relevant conclusions:

1. “Residential investment vehicles emerge as an innovative approach to encourage institutional investment in the residential sector. US residential REITs have successfully attracted large-scale institutional investment and enhanced the supply of dwellings (primarily apartments). However, affordable rental housing has largely been ignored by US REITs^[15]”.

2. “There is mixed evidence on the effectiveness of housing as an investment vehicle. Although the majority of studies referenced in this chapter support the potential of residential property in hedging the long-run inflation risk, no similar evidence is documented in the mixed-asset portfolio management context. Mixed-results have been found in relation to the role of housing in a mixed-asset portfolio”