We find that, in 2006, 29 percent of the workforce was required to hold an occupational license from a government agency, which is a higher percentage than that found in studies that rely on state-level occupational licensing data.

FORBES: Declining Union Membership Does Not Mean Declining Wages

Several studies have demonstrated that dementia patients given structured exercise programs and occupational therapy have a less severe decline in activities of daily living and improved quality of life.

CNN: Better understanding of dementia leading to more effective therapies

Within those categories, there are more than 100 sub-criteria, like degree of confinement in the work environment and income growth potential. (My colleague Jacquelyn Smith covered the last best and worst lists here.) The data come from the BLS, the Census Bureau, the Occupational Safety and Health Administration, and an array of private compensation surveys, trade association studies and state statistics.

FORBES: The Most Overrated Jobs 2012