1) The average cash-to-assets ratio for corporations more than doubled from 1980 to 2004. The increase was from 10.5% to 24% over that 24 year period. That was the findings of a 2006 study by professors Thomas W. Bates and Kathleen M. Kahle (University of Arizona) and René M. Stulz (Ohio State). When looking for an explanation, the professors found that the biggest was an increase in risk.
Indeed, the phenomena of corporate cash piling up has been going on for a long long time. You can date it back to the beginning of the great bull market in 1982 to 86, went sideways til the end of the 1990 recession. It has been straight up since then, peaking with the Real Estate market in 2006. The financial crisis caused a major drop in the amount of accumulated cash, but it has since resumed its upwards climb.
There is more at the link. As I've been saying, there is less to this issue than meets the eye.