Final answer:
You can check the insurance commissioner's office and healthinsurance.gov for data on market concentration in your state using the HHI.
Step-by-step explanation:
In order to determine if one insurance company controls the majority of the insurance market in Tennessee or your state of residence, you can refer to the insurance commissioner's office and the healthinsurance.gov site. These sources may have data on the market concentration in your state. By analyzing the Herfindahl-Hirschman Index (HHI), you can assess the level of market concentration. If the HHI is high, it indicates a highly concentrated market where one company controls a significant share of the market.