Aflac, the leading provider of voluntary insurance sales at the worksite in the U.S., announced that Daniel P. Amos, the company's chairman and chief executive officer, has been named to the Harvard Business Review's 2016 list of the 100 Best Performing CEOs in the World. Amos, listed at No. 32, moved up 37 places from 2015, when he was rated at No. 69. It is the second time that he has appeared on the prestigious list.

According to the Harvard Business Review, candidates are judged by the results they produce over their entire tenure, based on objective financial data. Researchers also rate companies' environmental, social and governance performance as a variable in their rankings, using two companies, Sustainalytics, a respected provider of ESG research, and CSRHub, another firm that collects and aggregates ESG Data.

To compile the list of world's best performing CEOs, HBR began with companies that were in the S&P 1200 at the end of 2015. Those that have been on the job for less than two years were not eligible. CEOs from 886 companies spanning 32 countries were ultimately analyzed, using daily financial data from the CEO's first day on the job until April 30, 2016. Three metrics, Financial Ranking and two separate ESG performance rankings provided by CSRHub and Sustainalytics, were used to compile a final ranking, with financial ranking weighted at 80 percent and each of the two nonfinancial rankings weighted at 10 percent.

In 2016, 33 new CEOs made the list, with 30 making it for a third time. On average, CEOs on the list became CEO at age 44 and have held their positions for 17 years.

Amos landed at No. 13 out of the 895 CEOs studied in the financial ranking. Since Dan Amos became CEO in 1990, Aflac has increased its dividend to shareholders every year, with revenues soaring from $2.7 billion annually to more than $20 billion today.

The company has also recently increased its focus on its primary philanthropic cause, childhood cancer, by sponsoring national events such as CureFest, which took place in Washington, D.C., on the National Mall. They also have conducted corporate social responsibility surveys in each of the past two years to help guide their CSR activities and ensure that their philanthropic goals are being met. In 2017, Aflac expects to make significant strides in energy conservation and other sustainability goals, as well, building upon an already robust and leading-edge program that has been recognized by Newsweek and Dow Jones.