Even with new jobless claims rising last week to their highest level since April, many economists say housing-related job losses may be a lot worse than official data show.First-time claims rose for a fifth straight week to 334,000, the Labor Department said Thursday, as the economy slows from its brisk pace in the second quarter.The four-week average of continuing claims rose to 2.561 million, the most since January 2006. "Jobless claims drifting up as they have is consistent with a slowdown" in GDP growth in the second half of the year, said John Silvia, chief economist at Wachovia. The uptrend...