1.425 million --That's how many people are in Long Island's labor force, the lowest figure since 2002. The decline from last year, 38,900, was the biggest numerical drop since 1990. The primary reason: the ever-increasing pace of retirements by baby boomers, experts say. Our graying population might stress our health care system, but the departure of boomers from the job market could be a boon for their children and grandchildren. Instead of looking to Florida, North Carolina and New York City, the jobs they need might be here.