Child Day-Care Services
Net profit margin rank: 10
Net profit margin: 10.43%
Change in 2009-2010 sales: 3.31%
Number of firms: 59,985
Employment: 853,648
The payroll-to-sales ratio was nearly 40 percent in 2006, before the recession, but dropped under 20 percent last year. That leanness boosted profit margins.