The Ministry of Justice and the Tribunal Service have published the quarterly usage statistics.
The report presents information on Tribunals Service activity for the third quarter of the 2010-11 year (1 October to 31 December 2010). Information for the same quarter of earlier years is also presented, as well as figures for previous quarters and previous years.
You have to delve quite deep into the report, but page 26 reveals some interesting information about age discrimination claims. You can see that for the first three quarters of 2010/11, the number of age discrimination cases was 5,700. This is more than in the whole of 2009/10 when the total number of age discrimination cases was just 5,200.
By comparison, the number of race discrimination claims over the same three quarters of 2010/11 was 4,700. Disability discrimination cases numbered 5,200.
So if these figure stay consistent, this will make age discrimination the second most common sort of discrimination (behind sex discrimination/equal pay.
The figures are available here (page 26).