Pending approval from its shareholders, Green Century Equity Fund said it will be able to continue its strategy of investing in the Domini 400 Social Equity Trust, the world’s oldest environmental and social index. Green Century has been investing in the index for over a decade.

Although the Domini 400 Index outperformed the S&P 500 since its 1990 inception, social screening, paying for the index, and the firm’s smaller size accounted for Green Century’s relatively high expense ratio. With approval from its shareholders, Domini switched to an active investing strategy this past April. If its shareholders approve, Green Century will be the only mutual fund involved in the newly transformed index created by KLD Research & Analytics, Inc. The partnership of KLD and Green Century unites two firms that helped lay the groundwork for socially responsible investing in the early 1990s.

“The Domini 400 Social Index has a 16-year track record of screening for socially and environmentally responsible investments,” said Douglas Phelps, chairman of the U.S. Public Interest Research Group, one of the nonprofit environmental advocacy organizations that founded Green Century, in a statement. “We felt it was important to continue offering this core equity holding to our current investors and to the broader investing public.”

In addition to these changes, Green Century reduced the total annual expense of the fund from 1.50% to 0.95%.