Is health care America's economic savior or scourge? The answer, strangely, might be both. In the short term, growth within the health-care sector provides a boost to a weak economy. But the same rise will eventually be more trouble than help. Over the last decade, the health-care industry has added 2.7 million to payrolls. Not only is that more than any single other sector, but the rise of health care explains half of all net job growth over the last decade. Health care has gone from 6.4 percent of the labor force in 1990 to 9.4 percent this month. Had the sector not expanded over that period, the unemployment rate would stand at 10.4 percent today, all else equal.