So those who doubt the swings in the yields of 90-Day T-Bills may want to look at the second chart which shows the volatility of the 90-Day Bill vs, the 2 year T-note. The white line on the chart is the 90-Day Bill and the yellow line on the bottom is the 2-year note. Again you see the volatility of the three month bill. One thing to see in the chart is the calamitous decline during he flash crash of the stock market in May when the bill plummeted and traded at a negative return. I'm working on he 30 chart and as soon as I get it I will forward it to you.