Paolo from Italy pointed out that the number of blog posts on OCaml has continued to increase in recent years (6,420, 10,500 and 12,100 in 2007/8/9 according to Google blog search) and referred to the success of this year's OCaml meeting with 80 delegates in France. These are certainly encouraging results but it may be worth bringing more data to the table.
Firstly, Google Trends can be used to graph the proportion of Google searches for different search terms over time. The following graph shows the trends for the keywords OCaml and F# since 2004:
As you can see, the proportion of searches for OCaml (blue) is in steady decline whereas the proportion of searches for F# (red) is on the increase and the two crossed over in 2007. In fact, we have found that Google Trends correlates very strongly with our revenue.
Secondly, we can examine statistics about the job market. The following bar chart illustrates the change in UK jobs from 2008 to 2010 for four functional programming languages (source IT Jobs Watch):
As you can see, every language saw tremendous growth in this boom period for functional programming except OCaml which actually saw a decline in the number of jobs on offer.
The deal breaker for us was, of course, revenue. The proportion of our revenue coming from OCaml has fallen steadily from 80% in 2007 to just 10% today.