How many French people live in London?

According to the BBC London is now France's sixth biggest city: "The French consulate in London estimates between 300,000 and 400,000 French citizens live in the British capital" which compares to city populations as follows:

• Paris - 2.3m
• Marseille - 859,000
• Lyon - 488,000
• Toulouse - 447,000
• Nice - 344,000

I've heard this kind of thing before and for some reason I've always liked this story (partly because as an urban economist I am interested in whether 'diversity' is one of the things that make cities work). But this morning I started to wonder if it is true.

The French consulate has 120,000 people registered with it but assess the real number living in the UK as 300,000-400,000 (this is the figure above). But according to the ONS there are 133,000 French nationals resident in the UK (for Oct 2010 - Sept 2011, see table 2.3). We are told that the ONS numbers are 'reasonably precise' (they have a standard error of about 8,000 giving a 95% confidence interval of plus or minus 16,000). Personally, I prefer the ONS numbers because at least we are told how they arrived at them.

So let's assume that all 133,000 are living in London (which is clearly a big assumption). Comparing this figure to the population of French metro-areas* makes London the 43rd biggest city in France. Even taking the French consulates estimates and comparing it to metro-areas puts London somewhere around 20th. Interesting, I suppose, but a little disappointing and certainly not as interesting as the BBC make out ...


*[Most urban economists (and the US census bureau) prefer the 'metro' to administrative numbers because they are more reasonably based on the 'functional' city - so Paris population is around 11m making it roughly the same size as London].