The U.S. is currently facing a severe shortage of doctors. The Association of American Medical Colleges predicts that by 2020, the shortage will amount to more than 90,000 doctors, including 45,000 patient care physicians. Why such a shortfall? The baby boom generation is getting older and will require more medical care in the coming years. The newly enacted Patient Protection and Affordable Care Act will soon require most people to obtain health insurance, leading millions more to seek care. Finally, a third of all doctors plan to retire this decade.

Read: States with the Fewest Doctors

Read: States with the Most Doctors

24/7 Wall St. looked at the 10 states with the highest ratio of patient care physicians and the 10 states with the lowest. The differences are stark. Massachusetts had 314.8 patient care doctors for every 100,000 residents. On the other hand, Mississippi had just 159.4, or just half the figure for Massachusetts.

States with a higher doctor-to-resident ratio share some common attributes. Generally, the states with high median incomes tend to have more doctors per capita, while poorer states tend to have substantially fewer. Among the 10 states with the most practicing physicians per capita are five of the six wealthiest states by median income in the country.

The ability to pay has a major influence on whether people have health insurance. Each of the 10 states with the highest concentration of doctors has uninsured rates lower than the national rate of 15.5%, while seven of the 10 states at the bottom have uninsured rates higher than the national rate. When doctors treat insured patients they are paid more than when they treat uninsured patients, incentivizing them to move to highly insured states.

“Most of [the uninsured] are choosing to not get insurance because they can’t afford it, and so you’re not likely to get paid, at least paid fully, from those patients,” AAMC’s chief policy officer Atul Glover told 24/7 Wall St. He notes that although the new federal health law will expand Medicaid coverage, the program, along with Medicare, tends to pay physicians between 30% and 40% less than private insurance companies.

Many of the states with high doctor-to-patient ratios also have a larger number of students who perform their residency in the state relative to the size of the population. This also signifies the ample medical facilities in which to practice medicine in the state. Six of the top 10 states are in the top 10 for the number of medical residents per 100,000 people. Meanwhile, six of the bottom 10 states are in the bottom 10 for medical residents.

A state’s doctor-to-patient ratio has significant consequences. The states with the most patient care physicians per capita also tend to be healthier states, and vice versa, Glover said. And statistics back that up. For instance, all but one state in the top 10 had a longer life expectancy than the country’s 78.6 years, with four of the states in the top 10 for life span. Meanwhile, all but two states in the bottom 10 had a shorter life expectancy than the national average, with five of the states in the bottom 10 for life span. States with high doctor-to-resident ratios tend to have lower smoking rates and fewer people who are either overweight or obese than those with low doctor-to-patient ratios.

Both medical schools and governments are trying to find solutions for the shortage of doctors. Some medical schools are expanding enrollment, although that is difficult to accomplish due to cutbacks in federal funds. Others state governments are considering programs that would pay patient care doctors to go to underserved areas for designated periods of time. This is similar to the National Health Service Corps., which will help pay off medical school loans for graduates who go to certain underserved states for two to four years.

Based on the American Association of Medical Colleges’ State Physician Workbook Data Book, 24/7 Wall St. determined the ten states with the most and least practicing physicians per 100,000 people. From the report, we also considered information on physician education, training and gender. All information from the AAMC is from 2010, and represents the most recently available data. 24/7 Wall St. also studied 2010 data on income, poverty and health insurance provided by the U.S. Census Bureau. Additionally,we reviewed data on life expectancy, obesity and other health factors from The Henry J. Kaiser Family Foundation.