Publication - Statistics

Scotland's marine economic statistics 2018

Statistics on the economic contributions of Scotland’s marine sectors in 2018. Includes a time series of Gross Value Added (GVA), turnover and employment for industrial categories defined as part of the marine sector.

74 page PDF

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74 page PDF

2.4 MB

Scotland's marine economic statistics 2018
17. Annex B: Methodology and source data

74 page PDF

2.4 MB

17. Annex B: Methodology and source data

17.1 Notes about tables

To prevent repetition of notes beneath each table, generic notes are presented in this section. Specific points about individual tables are noted as they arise in the report.  

Source data : Scottish Annual Business Statistics(SABS), Office for National Statistics,  Marine Scotland. Fishing and Aquaculture figures are taken from analysis of Marine Scotland statistics rather than the SABS figures. Table 32 summarises the main data sources for individual topics in this publication.  

Table 32: Source data for marine economic sectors
Economic sector and SABS SIC Code Data sources – economic measures
03.1: Fishing SABS data not used Seafish Fleet Economic Survey, Marine Scotland Sea Fisheries statistics 
03.2: Aquaculture SABS data not used Marine Scotland Aquaculture Survey statistics:  Shellfish Production Survey, and Fish Farm Production Survey Data Collection Framework (DCF) economic data[16]
09.1: Support activities for petroleum and natural gas extraction (extraction is not included in this publication) SABS  
10.2: Processing and preserving of fish, crustaceans and molluscs  SABS Seafish Processing Industry statistics – available but not used Number of Plants – Food Standards Agency
30.1: Building of ships and boats & 33.15: Repair and maintenance of ships and boats  SABS
42.91: Construction of water projects & 52.22: Service activities incidental to water transportation Marine tourism SABS
50.1: Sea and coastal passenger water transport 50.2: Sea and coastal freight water transport  SABS Transport Scotland statistics
77.34: Renting and leasing of water transport equipment  SABS
Marine tourism SABS various SIC codes (see Annex A) supplemented by geographic filters to select businesses within 100m of the coast line


  • Employment figures are head counts (not adjusted to Full Time Equivalents).
  • GVA and turnover values are adjusted to 2018 prices 
  • Since 2011, support activities for oil and gas were extracted using the SIC code  SIC 09.1: Support activities for petroleum and natural gas extraction. However, between 2008 and 2010 these figures were disclosive and so the wider code SIC 09 Mining support activities used to provide data. While there is little difference between the code values, it is important to note the change in coverage of the industry that is the largest contributor to the marine economy. The difference is minimal - see the Oil and Gas Methodology section.
  • Totals may not sum due to rounding and disclosure control.

17.2 Scottish Annual Business Statistics

The majority of economic figures in this publication have been taken from the Scottish Annual Business Statistics (SABS) publication. This provides data on a number of economic variables across a range of sectors, based on data from the Annual Business Survey (ABS) conducted by the Office for National Statistics (ONS). The SABS statistics were produced under partnership procedures between ONS and the Scottish Government. These have resulted in an improvement in the quality of the underlying data and consistency in the figures used by ONS and SG.

SABS data is attributed according to business site address e.g. a shop or factory, so data for a large company can be split over more than a single site. Rigorous checks are made to ensure that information relating to individual businesses are not disclosed, either directly or by deduction, in the figures released. In some cases this means that data cannot be presented at smaller geographies such as local authority areas.  

To set the individual industry results in context, throughout this publication they have been considered in the context of the Scottish economy as a whole. The national GVA estimate was taken from the Quarterly National Accounts of Scotland. The total employment in Scotland was taken from the Annual population Survey.

SABS data is used to monitor growth sectors in the Growth Sector Statistics Database. Figures from these Marine Economic Statistics are not directly comparable with the food and drink growth sector those in due to methodological differences.  

17.2.1 Sampling methodology

The ABS uses a register of businesses (the Inter Departmental Business Register (IDBR)) to produce an estimate of all businesses etc. that make up the population. The ABS sample is designed as a stratified random sample of UK businesses from the IDBR. The inquiry results are grossed up to the register population, so that they relate to all active UK businesses on the IDBR for the sectors covered.

Scottish Government also funds an enhanced ABS sample in Scotland, to improve the quality of Scottish figures. In 2018, around 2,600 extra firms in Scotland were sampled as a result of this boost, giving a total sample size in Scotland of around 8,300 firms

Scottish Annual Business Statistics are published as soon as possible after the release of ONS's regional results, which are due out each summer. In 2020 the SABS figures for 2018 were released in 24th June, 18 months after the end of the relevant calendar year.

SABS publish information about sample sizes and error margins for the survey.

17.2.2 Marine economic sectors

Marine economic sectors have been defined as those depending on the marine environment for their output, and where official statistics are available. The SABS data is used along with Marine Scotland's own statistical publications to gauge each industry's contribution to the Scottish economy. Where SABS is the sole source of data, the estimates are used directly. Where other sources are used the methodology is introduced in the relevant section of the report and explained more fully in this Methodology section.   

Economic values have been adjusted to take inflation into account and are presented at 2018 prices. This means that they are directly comparable in the time series tables.

17.3 Geographic Distribution

The distribution of the whole marine economy, excluding fishing and aquaculture (SIC code 3), by local authority was provided from SABS data. Values for fishing and aquaculture are not derived from SABS and were combined with the SABS extract to produce estimates of all marine economy at local authority level. The fishing values were distributed to local authorities as far as possible, with the residue, which could not be allocated, assigned to an 'unallocated' category. Aquaculture values were not available by local authority and therefore these values have been assigned as "Unallocated". 

The methodology used for this combining is the same as the previous bulletin but different from 2018 (2016 data). In the statistics for 2016 the SABS extract included aquaculture and sea fisheries statistics. However, in this report the economic statistics for fishing and aquaculture are not derived from SABS and so reconciliation was necessary for the economic values at local authority level.

17.4 Price presentation

All values have been adjusted to 2018 prices using the GDP deflators   making it simpler to compare values across a time series.

17.5 Sea Fisheries Methodology

The GVA and turnover estimates for the fishing sector were provided by Seafish as extracts from their Seafish Industry Authority Fleet Economic Survey[17]. Employment data was from Marine Scotland Sea Fisheries Statistics[18].

These sources provide a more reliable estimate of economic activity than the SABS figures, initially because Seafish use landings data as the source data for 'turnover' and carry out their own financial survey to produce estimates of GVA. The landings data is administrative data that covers the entire population rather than just a sample (as is the case with SABS), while the Seafish financial survey is stratified to produce a representative sample.  

Sample sizes

Marine Scotland publishes Scottish Sea Fisheries Statistics as an annual National Statistics publication. The statistics provide a detailed overview of the quantity and value of landings of sea fish and shellfish by Scottish vessels, and landings into Scotland. The Marine Scotland data is a census of all landings by Scottish registered vessels. Information on the Scottish fishing fleet and the number of fishers on Scottish vessels is also presented. Scottish Sea Fisheries Statistics are obtained by data extractions from Scottish and UK databases from data supplied by skippers.

The Seafish Industry Authority carries out economic surveys of the UK fishing fleet, published as annual Economics of the UK fishing fleet publications. The data is also available in the Seafish Fleet Economic Performance Dataset. This contains financial, economic and operation performance indicators for the period 2009-2019. The figures presented in this publication are an extract of economic performance data for all active vessels registered in Scotland.

The Seafish Fleet Economic Survey combines costs and earnings information from vessel accounts provided by vessel owners to the annual Seafish UK Fleet Survey, with official effort, landings and capacity data for Scottish registered vessels from Marine Scotland's Sea Fisheries Statistics. In 2018, the Seafish survey collected 370 sets of financial accounts for the UK fleet (8% of the active UK fleet).  

17.5.1 Regional data

Seafish provided figures at local authority level so that a regional distribution of the turnover and GVA can be presented. Data was allocated to the geography based on the location of the registration port of the vessel. Reporting at this level introduces the possibility of disclosing commercially sensitive information. To prevent this happening, all other segmentation categories were aggregated (species type, fishing gear etc.) and outputs where five or fewer vessels were registered were restricted.  

17.5.2 Seafish economic analysis methodology

Outputs from the Seafish Fleet Economic Survey provided fishing GVA estimation. Full details of the Seafish methodology are available in the Seafish Fleet Economic Survey, a summary is given here.  

The UK fleet is stratified into fleet segments using MMO data[19] on capacity, effort and landings for each vessel. For the data in this publication, only Scottish registered vessels were included and other segment criteria were suppressed.  

Financial accounts were collected for each fleet segment. 

Costs and earnings data from vessel accounts were allocated to fleet segments.

Fuel costs and crew costs are calculated differently from the other costs. For crew share, assign a minimum £100 per day, or the actual observed amount, whichever is the higher.  For fuel costs, estimate fuel consumption in litres and combine with the average annual red diesel price (excluding duty). 

Following calculation of fuel cost and crew share, apply the proportions from the other costs to the official declared fishing income for each vessel to calculate Gross Value Added, operating profit and net profit for each vessel.

UK fleet totals and fleet segment totals and averages are then calculated from the estimates produced for each vessel.

Where there are low sample sizes for a particular segment in a particular year previous years' estimates are taken into consideration.  

17.6 Aquaculture methodology

17.6.1 Source data

The quantity and value of fin and shell fish produced on Scottish aquaculture sites is sourced from the Marine Scotland Aquaculture Surveys. The aquaculture surveys are census surveys, receiving a response from every active fish farm in Scotland.    

The financial data is drawn from EU Data Collection Framework (DCF) data. The DCF sets out broad requirements for collecting social, economic and environmental data on aquaculture for the UK. The MMO acts as national correspondent for the data, and CEFAS collects the financial data for the UK. It is the DCF survey data that provided the source financial data for estimating the aquaculture GVA for Scotland.

For the reporting in this bulletin there was no EU call for data and so the responses were entirely voluntary. This explains the sample numbers, which are not large. The table below shows sample sizes for Scotland over four years of DCF surveys as collected by CEFAS.

Species Count of samples
  2013 2014 2015 2016 20171 2018
Mussels 12 9 5 5 4 3
Salmon 14 16 8 8 11 10
Trout 3 4 6 5 1 1
Total samples 29 29 19 18 16 14

1 Additional returns for 2017 (1 mussel, 1 trout and 3 salmon) were supplied at the same time as the 2018 return, so 2017 figures were updated.

17.6.2 Calculating GVA using DCF sample data and Marine Scotland survey data

1.  The DCF sample data contains financial returns for UK aquaculture businesses, by year and by species type. For this analysis, DCF data for Scottish production of salmon is used to represent finfish and mussels is used to represent shellfish. 

2.  Because the Marine Scotland aquaculture surveys are a census survey, the total production value can be assumed to estimate the value for Scotland. The DCF sample is scaled to Scotland level using the ratio of the DCF sample income to the Marine Scotland Aquaculture sample.  i.e.

The sample weighting is the Marine Scotland survey income divided by the CEFAS survey income.

3.  Estimate GVA by calculating, at the Scotland level, total outputs and total inputs. 

Gross Valued Added is the total output minus the total input

4.  Calculate the GVA to income ratio by 

The Gross Value Added to income ratio is Gross Value Added divided by Total output.'

This GVA to income ratio can be used to estimate annual GVA where the value of the production is known, e.g. for regional estimates. DCF data is available for 2013 to 2017 and a ratio is calculated for each of these years. Table 33 provides the unadjusted GVA and the GVA to income ration from 2015 onwards. To produce a longer time series, incorporating figures for before 2013, a mean GVA to income ratio was calculated and used to estimate the GVA from the known aquaculture turnover. This is noted in the tables.  

Table 33: GVA Ratios for aquaculture production
GVA GVA to income ratio
2015 6,083,167 0.59
2016 6,376,713 0.54
20171 8,810,641  0.68
2018 5,630,327  0.55
2015 98,314,541 0.15
2016 207,665,156 0.27
20171,2 413,385,470  0.38
20182 232,830,289  0.25
2015 3,842,184 0.15
2016 2,081,832 0.10

1 2017 figures updated following receipt of addition returns alongside the 2018 ones.
2 From 2017 Salmon covers all fin fish due to the small number of trout returns.

17.6.3 Comparisons with other data

SABS produces estimates for aquaculture GVA, turnover and employment. These have not been used because the aquaculture survey statistics are more complete than the ABS surveys. However, estimates for 2015 showed a considerable variance between SABS and estimates based on aquaculture data. This has been explored and the estimates in this publication seem to more accurately reflect the situation. In 2015, production was lower and costs higher due to biological problems such as sea lice and disease. This does not appear to have affected SABS survey estimates.

As with fishing estimates, aquaculture economic data has previously been reported in the Marine Scotland Economic Topic Sheet. The aquaculture method previously used a mean GVA to turnover estimate based on five years of SABS ratios. With the more specific data used for the estimates in this publication, individual years estimates for 2014 to 2018 are provided.  

17.6.4 Update to the 2017 aquaculture GVA

The DCF survey return data covers two years, the current year and the previous year. In 2020, the returns we received for 2018 that included some 2017 returns that had not been supplied the year earlier. One of these returns was from a large aquaculture company which had relatively low costs and a high income. These values were double checked with the company and it was confirmed that they were correct and that 2017 was a good production year. Therefore, the 2017 aquaculture data was updated to include these. This resulted in the GVA for 2017 increasing from the previously published figure. 

17.7 Oil & Gas support sector methodology

In this publication estimates for support activities related to oil and gas extraction are presented rather than the extraction itself. This retains consistency with National Accounts Statistics and ABS data where Oil & Gas extraction is normally allocated to a separate 'Extra Regio' category rather than allocated to a region within the UK

ABS data relating to Oil & Gas extraction (SIC 6) is allocated to UK regions (including Scotland) according to the address at which the business is registered - onshore and offshore Oil & Gas extraction and activities are allocated in this way. GVA associated with off-shore activity, under UK regional accounts procedures, is normally allocated to a separate 'Extra Regio' category rather than allocated to a region within the UK.

The codes used to produce figures related to oil and gas production have changed from 2009 to 2018.  

From 2009 to 2010, data was provided for SIC 09 Mining support service activities.  This included both SIC 09.1: Support activities for petroleum and natural gas extraction and SIC 09.9: Support activities for other mining and quarrying. While 'other mining and quarrying' activities are not necessarily marine, they were included because publishing only SIC 09.1 at the Scotland level would have been disclosive.    

Since 2011, only SIC 9.1 Support activities for petroleum and natural gas extraction have been included.  

Previous analysis has shown that SIC 09.9 'other mining and quarrying' is a small component of SIC 09. It is less than 0.02% of the employment, GVA or turnover of SIC 09.1 'Oil and gas services' and so the series has been considered comparable and no break in the series is required. Footnotes to tables explain this and in the Oil and gas methodology section the differences are explored.

17.8 Fish Processing Methodology

Seafish carries out annual financial surveys of a sample of majority sea fish processors and a biennial census of all UK fish processing businesses. Their  Seafood Processing Industry Report presents an overview and analysis of the UK seafood processing industry.  

While the Seafish report has the advantage of providing sector specific economic data and does provide information on sea fish processing only (SABS provides all fish processing), it has not been used in this publication because: 

The sample size for the financial data is small and not available at local authority level.

Employment is collected biennially and is provided as FTE for Scotland, so it is inconsistent with the headcount figures used in the rest of this publication.

17.9 Water Transport Geographic Distribution Methodology

SABS provides an estimate of the GVA for Scotland for both freight and passenger water transport. These estimates were used as the sole source for economic reporting in this publication.  

For the freight transport, DfT statistics provide a tables of tonnages of all freight traffic through UK major and minor ports. Using GIS, the Scottish ports were allocated to both Scottish Marine Regions (SMR) and Local Authorities which allowed an analysis of the geographical distribution of tonnage of freight. Passenger transport was not presented by specific ports and so no geographical breakdown was made.  

17.10 Marine Tourism Methodology

Marine tourism and recreation has been defined as including "activities which involve travel away from one's "habitual" place of residence, which have as their host or focus the marine environment and/or the coastal zone". This is the definition used in the 2015 Scottish Marine Recreation and Tourism Survey.

In this Marine Economic Statistics report, the estimates extract tourism that was identified as 'marine related' from all tourism figures as presented in the Scottish Annual Business Statistics data. The approach taken treats all tourism businesses located in postcodes within 100 metres of the coastline as engaging in marine tourism and recreation, or dependent on the marine environment.  

The list of SABS codes for relevant tourism and recreation business activities is provided in Annex A. This list aligns with SABS definitions of Sustainable Tourism in their Growth Sector Statistics. The methodology assumes that marine tourism and recreation businesses are located close to the coast. This assumption may exclude relevant activities of tourism and recreation businesses that are located within postcodes that are more than 100 metres from the coastline. The 100 metre threshold was selected to minimise chances of including in the estimates activities of non-marine tourism and recreation businesses that are located along the coast, especially in urban coastal areas such as Aberdeen and Edinburgh. 

A similar approach to estimating the economic contribution of marine tourism and recreation has been used by other EU member states such as Portugal and the Netherlands. The estimates in this report are therefore comparable with those produced by other countries. In addition, this methodology has been discussed with economists at the Oslo-Paris (OSPAR) Commission Socio-economic Working Group, and there is general agreement across member states on the principles of the approach.

In generating a geographic breakdown of the marine tourism sector, presenting the outputs by local authority was partially disclosive and Scottish Marine Regions (SMR) were selected as the lowest non-disclosive geography that could be used. While SMRs are developed strictly for information related to areas of sea within 12 nm of the coast, they were used in conjunction with the methodology described above to present both marine and land based tourism related to the sea.