Answer:
Apparently handing out a cash incentive for getting a job when you are unemployed really works. A 9% increase in the number of unemployed people getting a new job is significant.
But this hypothesis has a flaw. Is there any way that you can tell if people quit on purpose just to be able to file for unemployment and get the cash bonus? Unemployment benefits vary a lot depending on the state, but the national average is $378 per week. If you multiply that by 4¹/₂ weeks per month = $1,701 (roughly). It is not a fortune, but its not that bad either.
If we add the extra $500 cash bonus to the total unemployment benefits, in 15 weeks a person could earn $500 + (15 x $378) = $6,170 for not working.
It doesn't make sense for someone earning a high salary to quit just to get unemployment benefits, but being unemployed pays you $6,170 / (15 x 40 hours) = $10.28 per hour and that is more than the minimum wage.