Assets under management (AuM) of the world’s largest fund managers totalled $93.8 trillion in 2017, an increase of 15.6% compared to a year ago, according to a report from Willis Towers Watson’s Thinking Ahead Institute which analysed the top 500 managers.

The report found concentration of assets managed by the 20 largest managers at the highest level since 2000. The assets managed by them constituted over 43% of the total AuM of the largest 500 fund managers.

North America-based managers were found to represent the majority of assets at 58.1%. However, their share also reported a slight decrease, which marks the first drop since 2008.

Managers in Europe, Japan, and the rest of the world were found to represent 31.8%, 4.8%, and 5.2% of assets respectively.

While active assets accounted for bulk of the asset share at 77.6%, passive assets increased 25% on a year-on-year basis in 2017.

In the last five years, the share of passive assets was found to rise to 22.4% from 19.5%.

Thinking Ahead Institute head of research Bob Collie said: “Once again, total assets have increased; the rate of growth in 2017 is the biggest since 2009. The names at the top of the ranking are familiar names. There’s greater concentration in the biggest names.

“On the surface, the numbers might appear to tell a story of steady growth and of stability. But when you look at broader developments within and beyond the industry, there are signs that the industry is facing significant change.”