I assume most people would stay indoors and avoid the purge altogether. I'm also guessing that a good amount of people participating in the purge would only be looting which is what would concern me more as far as business and productivity goes. Unemployment rates could possibly be a thing of the past if there were a good number of deaths, but businesses would tank due to loss of stock. Anyone stealing whatever they wanted for free that day wouldn't be going out and buying those expensive items all year. Of course that means that businesses would likely just make sure they don't have any stock for people to steal, so there would likely be massive pre-purge sales. With nothing to steal, looters would likely just stay home at that point. I can't see a lot of people actually senselessly killing, even without any repercussions.