Executive pension plans sometimes grow to a hefty size, amounting to tens of millions of dollars, as extra retirement cushions for long-serving CEOs.

Then there's the record $159 million pension benefit of John Hammergren, the current chairman and CEO of drug distributor McKesson Corp. That's how much he would have received in a lump-sum payment had he voluntarily departed on March 31, McKesson disclosed in its annual proxy filing on Friday.

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