To be fair, it can be difficult to tell, because it's hard.... You have a particular level of activity, let's say in children's physical participation or their participation in artistic and cultural activities. You may have a certain trend, but then you introduce the measure, and it's generally applicable. What's difficult in these cases is to try to tease out what changes in a trend can be due to a tax incentive and what can be due to other things.
I talked about charitable donations, for example. For charitable donations, different rates have applied to different people at different times. Because of that, you have some variation, and you can do analysis that allows you to determine—