Economic issues are at the heart of the argument over Scottish independence. This week the Guardian published a study by Glasgow University academics alongside a separate investigation into how much of the wealth generated by four major Scottish industries - salmon, whisky, oil & gas and financial services - is kept in Scotland.

Below are details of the calculations that went into our findings on the Scottish financial services industry, which found that companies owned and registered in Scotland account for only one third of UK revenue generated by the Scottish financial services sector. First, the numbers, followed by a longer explanation of our workings and a brief history of the sector.

UK sales in £m

Top 10 pure Scottish companies: 17,564.4

Medium pure Scottish companies: 86.9

(Sub total: 17,651.3)

UK and overseas top 10 companies: 32,906.2

UK and overseas medium companies: 1,172.0

(Sub total: 34,078.2)

TOTAL: 51,729.5

Global net assets in £m

Top 10 pure Scottish companies: 34,591.8

Medium pure Scottish companies: 132.6

Small pure Scottish companies: 14.7

(Sub total: 34,739.1)

UK and overseas top ten companies: 65,409.6

UK and overseas medium companies 2,808.9

(Sub total: 68,218.5)

TOTAL: 102,957.6

Breakdown of analysed population by number

UK and overseas companies in Scotland with no Scottish registered office: 93

Pure Scottish companies with UK revenue in excess of £100m: 7

Pure Scottish companies with UK revenue less than £100m: 31

Pure Scottish companies filing abbreviated or exempt accounts: 79

Overseas companies with UK revenue in excess of £100m: 17

Overseas companies with UK revenue less than £100m: 23

TOTAL: 250

Top 10 non-Scottish controlled companies

The following shows each company's UK revenue in £m, and its ultimate controlling party

Royal Bank of Scotland - 16,541 - HM Treasury, London

Aviva Insurance * # - 4,111 - Aviva, England

Scottish Equitable* - 4,924.2 - Aegon, Netherlands

Prudential Retirement Income - 2,700 - Prudential, England

Kames Capital - 2,134 - Aegon, Netherlands

Clydesdale Bank - 810 - National Australia Bank

Tesco Personal Finance - 643 - Tesco, England

Prudential Distribution - 515 - Prudential, England

Aegon UK Corporate Services - 325 - Aegon, Netherlands

Royal London Pooled Pensions - 203 - Royal London, England

TOTAL: 32,906.2

Notes:

*Excludes investment returns

# Aviva figure struck after deducting revenue from Aviva International subsidiary

Top 10 Scottish headquartered, registered and controlled companies

UK revenue £m

Bank of Scotland 7654

Scottish Widows 7225

Standard Life* 1402

Baillie Gifford ^ 555

Aberdeen Asset Management 429.9

Scottish Friendly 129

Alliance Trust 116

Noble Grossart 33

Quayle Monroe 10.3

Dunedin 10.2

TOTAL: 17,564.4

Notes:

*Excludes investment returns

^Baillie Gifford estimate based on grossing up revenue from three registered companies in proportion to total assets under management

One of the most difficult challenges facing the Scottish electorate is the absence of an independent source of information to cross reference the claims made by the yes and no campaigners. Nowhere is this more apparent than the financial services sector, where it is difficult to define both its composition and size.

The most recent official data came from the Office of National Statistics' 2010 regional survey, which suggested that the financial services sector contributed around £8bn to Scottish GDP. Academics, however, are already divided on how to measure the GDP attributed to financial services companies and accept that it is extremely difficult to measure the contribution with confidence.

Against that backdrop, there is no independent source that sets out precisely what relates purely to Scotland. There are further issues in identifying precisely what constitutes the Scottish financial services sector (SFSS). Contributors to the SFSS range from major global financial institutions to small individual traders. Some contributors are headquartered and registered in Scotland, while others operate extensively in Scotland as part of a company's general UK operations.

In the light of these limitations, the research was structured to provide the most comprehensive picture yet of the shape, nature and ownership of the SFSS. The prime focus of the analysis was on UK sales, which are generally identified in the accounts of those companies required to file a profit and loss account at Companies House. It is widely accepted that there is a high level of integration between the SFSS and the rest of the UK. It is estimated that 90% of SFSS customers are based outside of Scotland.

It is accepted that the analysis cannot accurately replicate the data used to measure the GDP generated by the SFSS. However, it provides a comprehensive independent assessment of the ownership of Scottish registered SFFS companies and the levels of UK revenue they generate.

The source population for analysis was the National Library of Scotland's listing of Scottish company websites in the financial intermediation industry sector. This lists 429 businesses identified as operating in Scotland. This list was then cross-referenced for completeness to members of Scottish Financial Enterprise, the representative body for the SFSS, whose members account for 80% of those employed in the sector.

The analysis excluded firms that specialised predominantly in accountancy and law. Charities and public bodies were also excluded, as were estate agents and property development companies. Investment trusts were analysed but ultimately excluded, because of their reliance on the performance of global financial markets. The asset managers of these trusts were for the main part captured elsewhere in the analysis, the trusts had barely any employees and pure Scottish trusts were matched by those owned overseas.

The remaining companies were then split into three different categories. Overseas companies with only with registered companies only in England and Wales, overseas companies with Scottish-registered subsidiaries and "pure" Scottish companies. Overseas companies are defined as those with registered companies only in England and Wales within the group, although the ultimate owner may be registered abroad. A pure Scottish company is defined as:

• Scottish-registered

• Headquartered in Scotland

• And ultimately controlled by a Scottish-registered company.

The overseas companies with registered companies only in England and Wales were cross-checked with Companies House to identify any possible Scottish-registered companies elsewhere in the group.

The Scottish-registered companies were analysed by UK revenue and total net assets.

A potted history

The picture painted of the SFSS by this wideranging analysis is one of an industry that has been changed by the times rather than moving with them.

A quarter of a century ago, Scottish financiers and fund managers were held in awe and respect as the representatives of some of the most powerful financial institutions in the world. Today, they are still respected but no longer with such awe.

Two Scottish clergymen invented life insurance in 1748 through the Scottish Ministers Widows Fund. In the 1870s Robert Fleming invented investment trusts in Dundee as he sought to create an outlet for the wealth created by the city's jute merchants. The Bank of Scotland was created in 1695 not to provide credit for national government, but to meet the needs of households.

Inherent innovation was supported by excellence in implementation. The reputation was well deserved, but not preserved. Perhaps excellence gave way to complacency. In the early 1900s the financiers and other professionals began to take over Charlotte Square, the jewel of Edinburgh's new town. Originally the buildings were the magnificent homes of the landed gentry, but by the 1950s the square had become almost exclusively commercial.

The powerful Scottish fund managers who controlled the destiny of the myriad companies whose shares they owned were nicknamed the Charlotte Square mob. As the UK corporate sector embarked on an orgy of mergers and takeovers in Thatcher's 1980s, the Charlotte Square mob became ever more powerful in shaping the industrial landscape.

In some ways Charlotte Square mirrored the gentleman's club mentality that shaped London's Square Mile, where privilege and connections threw a protective net around the most cosy and financially rewarding of lifestyles.

But the City of London was in for a shock. Thatcher's assault on its old boys gave rise to the big bang of 1986, which saw cartels shattered and markets opened up as open outcry dealing gave way to electronic trading. The floodgates were opened to overseas marauders who raided the City to secure their slice of the lucrative London market.

As London came to terms with the turmoil of the big bang there was no such shock in Edinburgh, which largely looked on at a distance in benign amusement. As primarily asset managers rather than share traders, the immediate impact appeared to pass Scotland by.

But the big bang was actually shorthand for the globalisation of capital markets. With big US and Japanese banks staking their claim in London, the Stock Exchange moved overnight from private lunch club to a high pressure 24-hour trading cauldron.

Corporate executives still trekked to Scotland meet the fund managers who continued to hold court and wield immense power, the more astute observers began to question whether Scotland could retain its pre-eminence in a financial world that was changing dramatically and rapidly.

The SFSS was no stranger to consolidation, but on its own terms. For once innovation was absent and it was the Scots who were slowly being forced onto the back foot. The sector was beginning to follow trends, not set them. Those trends suggested that financial markets were being integrated on a global scale. The Scottish institutions saw this and recognised the trend

should be embraced.

In the 1990s the Charlotte Square mob began to disband as companies made their way to more modern and practical buildings. In 1993 Aegon of the Netherlands bought a 40% stake in Scottish Equitable, and took complete control in 1998. In 1997 The Prudential bought Scottish Amicable for nearly £3bn. Two of Scotland's most powerful institutions were no longer Scottish-owned. As the new millennium dawned it was questionable whether a standalone SFSS needed or wanted to survive.

It is a supreme irony that Charlotte Square now houses Scotland's first minister. Alex Salmond's claims about the contribution the sector makes to the Scottish economy seem out of kilter with the reality of the underlying economic structure.

The analysis shows that the 15 biggest Scottish-registered companies accounted for 97% of all UK sales generated by Scottish-registered companies. But 10 of those companies are owned either overseas or in England.

The SFSS is already fully integrated into the global financial system. Scotland, like the rest of the world, is dominated by a decreasing number of global players.

It is perhaps significant that two of the largest pure Scottish companies, Standard Life and Alliance Trust, have both said they will explore setting up English-registered companies in the event of a yes vote. This is perhaps not a comment on political independence, but a recognition that financial independence is no longer practical in an integrated international financial market.

It is also significant that the three Scottish banks empowered to issue banknotes are no longer independent. Royal Bank of Scotland is controlled by the British government, Bank of Scotland is owned by Lloyds and Clydesdale by National Australia Bank.

It has been acknowledged that there is a great financial interdependence between Scotland and the rest of the UK. Ninety percent of the customers of Scottish institutions are based outside Scotland, 80% of pensions and 70% of ISAs owned by Scots are provided by non-Scottish companies.

That interdependence has created a top heavy sector with the biggest players totally dominant. Seventy-nine of the 147 pure Scottish companies were so small that they are not required to produce

a profit and loss account. Of the next 28 medium-sized companies, not one had annual UK sales in excess of £10m. Meanwhile 30 of the 40 Scottish-registered companies controlled in England or overseas had turnover above £10m and 17 in excess of £100m. Only seven pure Scottish companies had UK sales in excess of £100m.

The analysis suggests that financial institutions based in Scotland are powerful global, not Scottish, organisations. Times have changed, and the days when just being Scottish counted for a lot in the financial sector have passed.