Happy to report a significant bit of progress. Vending machines of most kinds, pop, coffee, candy and snacks and even ticket, have a much higher acceptance rate of dollar bills these days. Several years ago the rejection rate of a dollar bill straight from the pocket to the bill receptacle was around 1:2. Lately the rate has been recorded at around 1:10. Not sure if this is a result of loosened standards or of better recognition technology. Good news either way. If its a result of the former it suggests evidence of a flourishing trust - fodder for another study. If its the latter, it suggests we understood the frustration so many of us felt for so many years and someone got to work fixing the problem. The downside; I think this puts the trope of the hapless office worker / student / spy being pwned by a vending machine that won't take a dollar bill and puts the poor sot through a series of machinations to appease the machine to rest.