Auto-Owners enjoyed another tremendous year in 2021. Much like 2020, our associates continued to provide excellent service to agents and policyholders, with many working primarily from home in light of the pandemic.
Auto-Owners achieved a record 10th consecutive profitable year in 2021. On top of that, the annual increase in premium was nearly $510 million, an improvement from 2020. We were fortunate to receive nearly $1.2 billion in new business from the many outstanding independent agents who represent us. This was split fairly evenly between personal lines and commercial lines.
In-force policy count grew by more than 62,000, bringing the total number of policies in force to more than 5.43 million. With the help of another excellent year in the stock market, policyholder surplus increased to more than $15 billion. We have the capacity needed to support all of the good business the agents have to place with us in 2022, and for years to come. Auto-Owners Life Insurance Company had another excellent year as well.
Auto-Owners was once again recognized by AM Best for our strong performance and financial strength. Our A++ (Superior) rating was reaffirmed, making it 50 consecutive years we have received the highest available rating given out by AM Best.
Atlantic Casualty Insurance Company, our excess and surplus lines subsidiary, enjoyed another outstanding year of profitable growth. This was recognized by AM Best, which upgraded Atlantic Casualty's financial strength rating from A to A+. Concord General Mutual, our affiliate operating in the four northern-most New England states, also grew profitably in 2021. Capital Insurance Group, acquired in 2019, experienced vastly improved results in 2021, generating an underwriting profit.
It is a privilege for me to work with our hard-working associates, showing agents that no carrier can partner better with them when it comes to taking care of policyholders.