Still, even the year-over-year data (which make seasonal variations irrelevant) look impressive. The economy added 1.6 million jobs from December 2010 to December 2011, according to the latest estimates. Some economists, however, believe this is also exaggerated. The job-count numbers are based on payroll samples via unemployment insurance reports. But those, too, are subject to error. We'll get a much better picture of 2011 next month, when the Labor Department trues up its job-growth with more complete payroll counts.