06/01/2015 13:31 GMT | Updated 08/03/2015 05:59 GMT

10 Things You Need to Know Before You Estimate The UK Sex Industry's Contribution to Gross Domestic Product

1. In 2012 the UK's Office for National Statistics (ONS) estimated that sex workers contributed £5.7billion to the economy. This calculation was produced in response to an EU demand that 'prostitution and illegal drugs' should be counted as part of a country's gross domestic product.

2. The ONS estimates that about 61,000 are employed as sex workers in the UK.

3. The scientist and author Brooke Magnanti disagrees. In June of last year she reported that the ONS got the figure of 61,000 from Eaves for Women, a charity that has been heavily criticized for its dubious statistical research in the past.

4. The ONS also priced the average cost per visit to a sex worker at about £67, a figure that appears to be a guestimate based on average fees charged by escorts on PunterNet, a website which is considered to represent higher income sex workers.

5. The ONS estimated that each sex worker sees about 23 clients per week and works 52 weeks a year. Based on this total, the average sex worker would turn over about £100,00 and would see around 1,200 clients a year.

6. The ONS figures suggest that there are a total of just under 75million visits to sex workers every year in the UK, or nearly 1.5million visits a week. This figure seems completely implausible when judged against data from the UK National Survey of Sexual Attitudes and Lifestyles (NATSAL 3) which was carried out between 2010 and 2012. NATSAL figures found that just 3.6% of men aged 16-74 had paid for sex in the past 5 years.

7. However, the ONS chose to ignore British research and instead, estimated the number of clients based on research conducted in the Netherlands, a country where sex work is legal and heavily regulated. In the UK selling sex is legal, but brothels are not, and nor is street walking, so people who sell sex are still routinely criminalized, and are, therefore, highly unlikely to be working fifty two weeks of the year, let alone seeing 1,200 hundred clients.

8. Concerned about the multitude of distortions in the ONS figures, Magnanti contacted the ONS to ask them why they had not done their research more carefully. She was told that time pressure meant that they didn't have time to contact 'experts'.

9. Why would the ONS concoct figures from dubious research when they knew that it would inflate the financial contribution of the sex industry and increase the size of our bill to the European Union?

10. Turns out there are a lot of organisations in the UK who have a vested interest in inflating the scale of the sex industry, simply because it helps them to secure funding. For example, in 2010, the Eaves charity which supplied the ONS with the total estimate for the number of workers in the sex industry, had an income of over £5million, yet their annual report shows that between April 2009 and March 2010, just 50 out of 138 referred women received accommodation and support and just 80 women received outreach support. In April 2011, Eaves lost their public funding. There was no explanation for the cut, but five million quid to help one hundred and thirty women? You do the math.