Direct Bidder Percentage used in the chart was calculated from the auction results published by the US Treasury Department. For bills, the 1st week of the month data were used. For notes, the July auctions will be held next week. The first-ever auction of 7-year note was February 2009.
Many analysts and observers have noted the increased Direct Bidder participation in Treasury notes and bonds. However, the same is also true for shorter bills, as you can see in the chart.
There are a few volatile data series (2-year note, 7-year note), but the general average trend of Direct Bidder participation in Treasury auctions started to move up in February 2010. Notice that after April most Treasury securities featured here have over 10% Direct Bidder participation.
Events that may have influenced the trend:
In late January, the SEC announced new rules for money market funds. Money market funds would be required to hold certain percentage of safe and liquid securities such as Treasuries.
In early March, the SEC announced the implementation dates (end of May, end of June) for the new money market fund rules.
The Federal Reserve ended the quantitative easing on March 31.