In his 2011 book "Debunking Economics: The Naked Emperor Dethroned?", Steve Keen says:
I am curious about the "falling student enrollments" claim. Is this true? I have struggled to find good information online. In many places one doesn't study economics alone, but business, so data is tricky to analyse. For instance, here are some stats on business enrollment at the undergraduate level in the US, showing no net fall in numbers. The little I could find for the UK also shows recent increases. Same for Canada. Australia saw a fall between 1989 and 2001 in "Society and Culture" (which includes economics) but fairly stable afterwards (see Figure 2.5). OECD data between 2013 and 2016 doesn't show a consistent fall in social sciences or business studies across countries (although data is only in terms of percentages).
So, based on poor stats above, it seems the remark by Keen is not right. Any better data on this?