State Street Global Advisors (SSGA), the asset management business of Boston-based State Street Corp. on Thursday announced recent updates to the composition of its SSGA Gender Diversity Index.

The index, first launched in March 2016, is a quantitative index driven by the highest percentages of women on boards and in senior leadership positions at a given company within their sectors, and tracks U.S. exchange-listed large capitalization companies that meet those criteria.

After the annual rebalance on July 15, 61 new companies were added to the index, which now has 171 constituents. The top 10 companies held in the market capitalization weighted Index are Pfizer Inc., Coca-Cola Co., PepsiCo, Inc., International Business Machines Corp., Mastercard Inc. Class A, Amgen Inc., McDonald’s Corp., U.S. Bancorp, CVS Health Corp. and Lockheed Martin Corp.

“We applaud the new additions to the SSGA Gender Diversity Index for their efforts in confronting the gender diversity challenge by hiring and retaining women in senior leadership,” says Ronald O’Hanley, president and CEO, SSGA, in a statement.

“Companies in the index have demonstrated a track record of employing women in their senior management ranks,” adds Lynn Blake, chief investment officer for SSGA’s global equity beta solutions. “By focusing on U.S. companies that have the highest percentages of women in senior leadership positions relative to their sector peers, we designed this Index to reflect companies that are committed to gender diversity.”