In the world of investing, the amount of data to factor into the purchase of a stock can be overwhelming. Researching quarterly earnings calls, 10-Ks, P/E ratios, and valuations is all important. But as important as the financial aspects of a company are, they shouldn't be the only credentials up for consideration. The leadership, culture, and diversity of that company all have an important part to play in whether it succeeds or not.

A recent Calvert Investments report considered the diversity of companies in the S&P 100. Calvert ranked the companies based on 10 different diversity criteria, including Equal Employment Opportunity policies (EEO), internal and external diversity initiatives, highest-paid executives, board diversity, director selection criteria, and the company's commitment to overall diversity.

In its study, Calvert defined diversity as: "nondiscrimination and equal opportunity concerning recruitment, hiring, pay, promotion, training, and tenure without regard to race, gender, age, religion, national origin, ethnicity, sexual orientation, gender identity and expression, HIV/AIDS status, medical status, and mental and physical ability."

According to Calvert's research, here are the four most diverse companies in the S&P 100:

1. Citigroup (C 0.26%) -- Diversity score of 100: Part of Citigroup's perfect score comes from its diversity policy that is both specifically stated and implemented through programs with measurable metrics. Citigroup is one of just six companies in the S&P 100 that have two minorities in the five highest-paid positions, and one of seven companies with a minority CEO at the time of the study.

The company is also one of 33 companies in the S&P 100 to publicly support the Employee Non-Discrimination Act, or ENDA. While 96 companies out of the 100 in the report have a nondiscrimination policy based on sexual orientation, ENDA is Congressional legislation that would offer universal protection against sexual orientation discrimination for civil and nonreligious companies with more than 15 employees.

In addition to this, Citigroup discloses all of its federal EEO-1 data. The data includes company counts of ethnicity, race, and gender, and Citigroup divides that demographic information into the company's job categories for a full picture of diversity.

2. Merck (MRK -0.11%) -- Diversity score of 100: Merck tied with Citigroup for the top diversity spot in the study. Like Citigroup, Merck has a full EEO-1 data disclosure policy, publicly supports ENDA, and also has two minorities in the top five paid positions. The company also received part of its high diversity ranking because it has a minority CEO, a trait that only six other S&P 100 companies share.

Merck also implements the United Nation's Women's Empowerment Principles, a set of guidelines for businesses to promote women in the workplace, marketplace, and communities. The principles include everything from promoting leadership opportunities, health and safety, education, and data reporting on gender equality. Merck is one of only six S&P 100 companies to sign the initiative.

3. Coca-Cola (KO 0.68%) -- Diversity score of 95: Coca-Cola earned the second-highest rating in the report, partly due to its board's Public Issues and Diversity Review Committee. The committee reviews how well the company meets its diversity goals and is chaired by a minority board member.

The Coke maker also publicly supports ENDA, and is one of just six S&P 100 companies to sign the UN's Women's Empowerment Principles initiative. In addition, Coca-Cola also has two minorities in the top five highest-paid positions in the company. The company discloses the gender and ethnicity breakdown of its employees for its headquarters, North American offices, and global workforce on its website, and has its own publicly available diversity report as well.

4. JPMorgan Chase (JPM 0.65%) -- Diversity score of 95: JPMorgan ties for second place with Coca-Cola, and just like the Coke maker, it publicly supports ENDA. The company also has two women in the five highest-paid positions, which include the Chief Executive Officer of Asset and Wealth Management and the Chief Financial Officer. On its 11-member board, two of the seats are held by women and one is occupied by a minority male.

The fact that JPMorgan Chase made it to the top four of the Calvert list isn't surprising considering it won the Securities Industry and Financial Markets Association's Team Diversity Leadership Award for the company's Black Organization for Leadership Development initiative back in October. BOLD provides JPMorgan Chase employees of African descent with professional and personal development programs.

Investing in the future
Diversity isn't likely to be the only factor you weigh when making an investment decision, but it should be considered along with the company's culture and leadership. In the end, Foolish investors are looking for great companies with stellar attributes that they can hold on to for long-term gains. And a well-represented workforce should be part of that pursuit.