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Lighting up cigarettes has gradually become less common in Minnesota, yet a recent study reveals smoking's decline has been slower in poorer counties.

Smoking has decreased all across the country, according to a recent study by the Institute for Health Metrics and Evaluation , but at much slower rates in areas with lower average income. Data analyzed by IHME was broken down by county spanning the years 1996 to 2012, revealing trends in every state, including Minnesota.

Without drilling down into data on the county level, big metro areas can dominate state-level research, said Dr. Ali Mokdad, a University of Washington Professor and researcher on the study.

"You will miss the real issues," he said.

Smoke Prevalence by county over time