Do ignition coil replacement problems track solo operators as a share of all auto repair businesses across states?

Across U.S. states, NHTSA owner complaints about ignition coil replacement run higher where solo operators as a share of all auto repair businesses is higher, after adjusting for the makes sold in each state. This is an association across states, not proof that solo operators as a share of all auto repair businesses causes this repair.

How to read it: Each dot is a state. Further right means more solo operators as a share of all auto repair businesses; higher up means more complaints for this repair than expected (1.0 is average). If the dots climb to the right, reports of this repair rise with solo operators as a share of all auto repair businesses.

What it shows: States with more solo operators as a share of all auto repair businesses tend to sit higher on the chart across 28 states: a pattern in the data, not proof of cause.

• The 9 states with the most solo operators as a share of all auto repair businesses (Georgia, Florida, Texas, Louisiana, Arkansas, Tennessee, Alabama, Kentucky, South Carolina): reports of this repair run 21% above what the makes sold there would predict, and 6 of 9 are above expected. The 9 with the least (Massachusetts, Washington, Connecticut, New York, New Jersey, Wisconsin, Michigan, Illinois, Colorado): 8% below, and 2 of 9 are above expected.
• Exceptions: Florida, Texas and South Carolina are among the highest in solo operators as a share of all auto repair businesses but report below expected.
• Split the states into thirds: the third with the least solo operators as a share of all auto repair businesses runs 8% below what the makes sold there would predict, the middle third 2% above, and the third with the most 21% above. It steps up steadily.
• For solo operators as a share of all auto repair businesses, after allowing for the 1562 comparisons we ran, luck alone would produce a pattern this strong about 1 time in 16. Take out any single state and the solo operators as a share of all auto repair businesses pattern still holds.
• Weak spot: compare only states with similar gallons of motor gasoline burned per resident per year and the pattern keeps about 37% of its strength, so part of it may come from gallons of motor gasoline burned per resident per year instead of solo operators as a share of all auto repair businesses.
• For solo operators as a share of all auto repair businesses, of the 4 exception states, 2 read the same way for the other parts of the system (so that is the system there, not this repair) and 2 are specific to this repair.

Where more repair work is done by one-person operators with low overhead, prices and the kinds of repairs done differ from chain and dealer shops.

Source: Census Nonemployer Statistics 2021 and County Business Patterns 2023, NAICS 8111, joined to NHTSA owner complaints · file downloaded 2026-10-06