See this Pew report, Natural Disaster Mitigation Spending Not Comprehensively Tracked. The subject title is a good summary of the findings. The bottom line is that we as a community of emergency managers are not good at collecting data and thus cannot tell our story. Not that mitigation would be the first chapter in any story written by emergency managers. We'd rather talk about disaster preparedness and the sexy topic of disaster response. Mitigation is only a priority when funding becomes available "post-disaster" when FEMA opens the checkbook.
Back to the topic of performance measurement — it is hard to do in our emergency management world, but we could at least count the dollars being expended. Money loosely translates into effort. Little money, little effort! It takes the episodic post-disaster mitigation funding to really open the federal purse. Without the federal funding — there would be little mitigation being done. There are few isolated state examples called out in the report, but they are few in number.
See the chart below that depicts the lopsided distribution of funds between pre- and post-disaster mitigation.