According to a report released by the Center for Retirement Research (CRR) at Boston College, most of the decline occurred in plans that had between 25% and 50% of plan assets in employer stock. In 2009, still two-thirds of KSOPs had more than 10% of assets in company stock, the statutory limit for defined benefit pension plans.
PPA2006 allowed participants in plans with employer stock who had at least three years of service to diversify their holdings (see IRS Extends Relief for Employer Stock Account Diversification). However, stand-alone ESOPs, those that do not allow employee elective deferrals or after-tax contributions, were exempt from this provision. The research found there was no change in holdings for stand-alone ESOPs.
The research used detailed Form 5500 financial data for stand-alone ESOPs and those that allow employee elective deferrals or after-tax contributions, or KSOPs, from 2003 to 2005 (before) and 2007 to 2009 (after) the PPA.
The report can be downloaded from http://crr.bc.edu/working_papers/the_pension_protection_act_of_2006_and_diversification_of_employer_stock_in_defined_contribution_plans.html.