I think part of it is that people were home this year and noticed the swarms. Another thing is we did almost nothing trying to control swarms in our yard. We had about 15 swarms, of which we were able to rescue about half (the others landed 40 feet up in the forest open space next to my yard. The ones we captured landed in lower trees. I bought a swarm trap to hopefully catch more of them next year, especially since I will be working again...).