This study reports on the estimated funded status of all U.S. multiemployer plans as of December 31, 2015, and shows the change in funding levels from June 30, 2015. The overall funding shortfall for all plans increased by $26 billion for the six-month period ending December 31, 2015, while the aggregate funded percentage decreased from 79% to 75%. For most multiemployer pension plans, estimated 2015 investment experience was flat or slightly negative, far below expected returns. Over one-half of the total underfunding for multiemployer pension plans continues to be attributable to plans that are less than 65% funded. Of the nearly 200 critical plans with 2014 information available, about 40% are projected to be insolvent at some point. About 200 funds have reduced their assumed rate of return over the past several years, typically by 0.25% or 0.5%.