P&I staff gathered the information for this report in three steps.
Questionnaires were sent to more than 1,200 fund sponsors in P&I's database. The largest 1,000 were identified from the completed questionnaires, follow-up phone calls and e-mails.
Data for funds that did not respond were culled from published annual reports and the Form 5500s filed with the Department of Labor.
In cases where no information was available from the fund, or the data obtained were older than as of June 30, 2010, P&I calculated estimates to Sept. 30, 2010.