I wonder what the criteria is for "poverty". A couple hundred years ago so many people lived in agricultural societies. Money wasn't as necessary because you grew your own crops, raised your own livestock, and didn't need money as much as we do today. I couldn't find anything in this study that accounted for possessions (property, houses, livestock, etc.) instead of just monetary wealth. So this change in our lives would definitely account for a large swing in poverty.
Just a thought that popped in my head.