A first-of-its-kind ranking of 401(k) plans at the 250 biggest companies in the U.S. found that ConocoPhillips and Abbott Laboratories are among those that provide the most lucrative retirement benefits. Among the least generous are Facebook Inc., Amazon.com Inc. and Whole Foods Market Inc. The natural-foods grocer offers a maximum contribution of $152 annually.

ConocoPhillips, a Houston oil and natural gas producer, topped the Bloomberg News rankings of the largest public companies’ 401(k) plans, largely due to a matching formula that contributes 9 percent of annual salaries for employees who save as little as 1 percent of their pay.