Steve Johnson noticed this bit about NASA's workforce in his longer piece on NASA and publicity
In related news, NASA has determined that 12 percent of its engineers and 21 percent of its scientists are now eligible to retire, and estimates that in 2011, 28 percent of its engineers and 45 percent of its scientists will be eligible to retire.
In case you work for a company where there is an impending wave of retirements, you probably have it much easier than does NASA. (Unless you work for a company that's making nuclear weapons -- not too much of that expertise in the younger generations.)
How to solve this dilemma is a worry of many a business leader. Lost knowledge has always been a problem, but the magnitude has changed significantly as the hiring practices of companies have changed in response to the winds of finance and economics.