A new study commissioned by CarInsurance.com suggests that of all the factors that go into determining car insurance rates, just five digits — your ZIP code — can have a surprisingly large impact.

In order to control for considerations such as gender, age, car model, driving record and financial history, the California-based website compared rates from six major Medicare agents near me providers for a hypothetical 40-year-old man driving his 2014 Honda Accord 12 miles each day (with a clean driving history and good credit).

The Motor City turned out to be the most expensive place for this driver to get coverage, with Detroit’s 48227 zone averaging an annual premium of $5,109. If that driver lived just over 100 miles south, however, he’d be living in the cheapest ZIP code in the country; in Green Springs, OH, the same coverage would cost only $647 on average. The national average came in at $1,231, and cities such as Palo Alto, CA, and Denver, CO, were closest to that figure.

Why does ZIP code factor so heavily into insurance rates? “Based on the number and severity of car insurance claims within the area, insurers assign ZIP codes different risk levels,” Michelle Megna, managing editor of CarInsurance.com, wrote in an explanation of the study’s findings. “Insurers take into account the frequency of thefts, collisions and vandalism to gauge the likelihood of such incidents happening to drivers within the ZIP code.”

The most expensive areas after Detroit were 11226 in Brooklyn, NY ($3,877 annually); 19132 in Philadelphia ($2,760); 02903 in Providence, RI ($2,760); and 70117 in New Orleans ($2,542).

The top five discount ZIP codes were rounded out by 28704 in Arden, NC ($671); 04072 in Saco, ME ($709); 24073 in Christiansburg, VA ($751); and 83706 in Boise, ID ($753).

It’s unlikely that drivers will move across the country to take advantage of some of these ultra-low rates. But it’s good for them to know that moving even a few miles can raise or lower premiums.