Considering Levi Strauss & Co.'s announcement this week that it's laying-off 5,900 employees in the U.S. and Canada, the company's second round of layoffs in a little over a year, and a growing sense in other industries that companies will try to do even more with the same number -- or fewer -- workers, is America's historically low unemployment about to rise? Yes, reveal data from Martin Regalia, chief economist at the U.S. Chamber of Commerce, Washington, D.C. He sees U.S. joblessness rising from a first-quarter 1999 annual rate of 4.5% to 4.7% in the second quarter and to 4.8% in the third and fourth calendar quarters. Merrill Lynch & Co. also sees unemployment increasing, but more modestly. Its forecasters anticipate a 4.4% jobless rate this quarter and next before a fractional rise to 4.5% in each of the two remaining quarters of 1999.