By SAM HANANEL The Labor Department says the number of workers who died on the job fell by 17 percent last year to the lowest level in nearly two decades.The 4,340 workplace fatalities recorded in 2009 was the smallest total since the Bureau of Labor Statistics first began tracking the data in 1992.The agency says high unemployment and layoffs in more dangerous industries like construction played a major role in the decrease.Workers on average logged 6 percent fewer hours last year than in 2008.