Union Members:Don't Read This A National Bureau of Economic Research study suggests the 2000 Firestone tire debacle was caused not so much by use of cheaper materials or inexperienced replacement workers during labor strife as by something about the regular workers themselves. Princeton University economists Alan Krueger and Alexandre Mas conclude that tires made at Firestone's Decatur, Ill. plant just before and after unhappy workers staged a strike suffered extraordinary failure rates. The researchers suggest more safety checks around walkouts. Some 14 million tires were recalled amid links to 271 deaths and more than 800 injuries. --Ira Carnahan