Nineteen years ago, Jennifer Courter set out on a career path that has since provided her with a steady stream of lucrative, low-stress jobs. Now, her occupation -- mathematician -- has landed at the top spot on a new study ranking the best and worst jobs in the U.S.

"It's a lot more than just some boring subject that everybody has to take in school," says Ms. Courter, a research mathematician at mental images Inc., a maker of 3D-visualization software in San Francisco. "It's the science of problem-solving."

The study, released Tuesday from CareerCast.com, a new job site, evaluates 200 professions to determine the best and worst according to five criteria inherent to every job: environment, income, employment outlook, physical demands and stress. (CareerCast.com is published by Adicio Inc., in which Wall Street Journal owner News Corp. holds a minority stake.)

The findings were compiled by Les Krantz, author of "Jobs Rated Almanac," and are based on data from the U.S. Bureau of Labor Statistics and the Census Bureau, as well as studies from trade associations and Mr. Krantz's own expertise.

According to the study, mathematicians fared best in part because they typically work in favorable conditions -- indoors and in places free of toxic fumes or noise -- unlike those toward the bottom of the list like sewage-plant operator, painter and bricklayer. They also aren't expected to do any heavy lifting, crawling or crouching -- attributes associated with occupations such as firefighter, auto mechanic and plumber.

The study also considers pay, which was determined by measuring each job's median income and growth potential. Mathematicians' annual income was pegged at $94,160, but Ms. Courter, 38, says her salary exceeds that amount.

The Best and Worst Jobs Of 200 Jobs studied, these came out on top -- and at the bottom: The BestThe Worst1. Mathematician 200. Lumberjack2. Actuary 199. Dairy Farmer3. Statistician 198. Taxi Driver4. Biologist 197. Seaman5. Software Engineer 196. EMT6. Computer Systems Analyst 195. Roofer 7. Historian 194. Garbage Collector8. Sociologist 193. Welder9. Industrial Designer 192. Roustabout10. Accountant 191. Ironworker11. Economist 190. Construction Worker12. Philosopher 189. Mail Carrier13. Physicist 188. Sheet Metal Worker14. Parole Officer 187. Auto Mechanic15. Meteorologist 186. Butcher16. Medical Laboratory Technician 185. Nuclear Decontamination Tech17. Paralegal Assistant 184. Nurse (LN)18. Computer Programmer 183. Painter19. Motion Picture Editor 182. Child Care Worker20. Astronomer 181. Firefighter More on the Methodology For methodology info and detailed job descriptions, go to http://careercast.com/jobs/content/JobsRated_Methodology

See the complete list of job rankings

Read about the last study of the best and worst jobs. 1. Mathematician 200. Lumberjack2. Actuary 199. Dairy Farmer3. Statistician 198. Taxi Driver4. Biologist 197. Seaman5. Software Engineer 196. EMT6. Computer Systems Analyst 195. Roofer 7. Historian 194. Garbage Collector8. Sociologist 193. Welder9. Industrial Designer 192. Roustabout10. Accountant 191. Ironworker11. Economist 190. Construction Worker12. Philosopher 189. Mail Carrier13. Physicist 188. Sheet Metal Worker14. Parole Officer 187. Auto Mechanic15. Meteorologist 186. Butcher16. Medical Laboratory Technician 185. Nuclear Decontamination Tech17. Paralegal Assistant 184. Nurse (LN)18. Computer Programmer 183. Painter19. Motion Picture Editor 182. Child Care Worker20. Astronomer 181. Firefighter

Her job entails working as part of a virtual team that designs mathematically based computer programs, some of which have been used to make films such as "The Matrix" and "Speed Racer." She telecommutes from her home and rarely works overtime or feels stressed out. "Problem-solving involves a lot of thinking," says Ms. Courter. "I find that calming."

Other jobs at the top of the study's list include actuary, statistician, biologist, software engineer and computer-systems analyst, historian and sociologist.

Mark Nord is a sociologist working for the Department of Agriculture's Economic Research Service in Washington, D.C. He studies hunger in American households and writes research reports about his findings. "The best part of the job is the sense that I'm making some contribution to good policy making," he says. "The kind of stuff that I crank out gets picked up by advocacy organizations, media and policy officials."

The study estimates sociologists earn $63,195, though Mr. Nord, 62, says his income is about double that amount. He says he isn't surprised by the findings because his job generates little stress and he works a steady 7:30 a.m. to 4 p.m. schedule. "It's all done at the computer at my desk," he says. "The main occupational hazard is carpal tunnel syndrome."

On the opposite end of the career spectrum are lumberjacks. The study shows these workers, also known as timber cutters and loggers, as having the worst occupation, because of the dangerous nature of their work, a poor employment outlook and low annual pay -- just $32,124.

New protective gear -- such as trouser covers made of fiber-reinforcement materials -- and an increased emphasis on safety have helped to reduce injuries among lumberjacks, says Paul Branch, who manages the timber department at Pike Lumber Co. in Akron, Ind. Still, accidents do occur from time to time, and some even result in death. "It's not a job everybody can do," says Mr. Branch.

But Eric Nellans, who has been cutting timber for the past 11 years for Pike Lumber, is passionate about his profession. "It's a very rewarding job, especially at the end of the day when you see the work you accomplished," he says. Mr. Nellans, 35, didn't become discouraged even after he accidentally knocked down a dead tree and broke his right leg in the process four years ago. "I was back in the woods cutting timber in five weeks," he says.

Other jobs at the bottom of the study: dairy farmer, taxi driver, seaman, emergency medical technician and roofer.

Mike Riegel, a 43-year-old roofer in Flemington, N.J., says he likes working "outside in the fresh air." Since he runs his own business, which he inherited from his father, he can start and end his day early in hot weather or do the opposite when it's cold.

The study estimates roofers earn annual incomes of $34,164, which Mr. Riegel says is consistent with what he pays new employees. Roofers also ranked poorly because of their hazardous working conditions. "You obviously can't be afraid of heights," says Mr. Riegel, who once fell two stories while working on a rooftop in the rain but luckily landed safely on a pile of soft dirt. "I missed some cement by 10 feet."

Write to Sarah E. Needleman at sarah.needleman@wsj.com