A study conducted by Pensions & Investments (P&I) and consultants Towers Watson showed that the combined assets of the world's top 300 pension funds are now worth over $15 trillion.

Towers Watson is a global professional services company which has more than 16,000 associates around the world to date.

In a report published by Reuters, this growth is attributed to the spur of retirement saving of aging populations both in North America and Europe as the governments provided incentives to encourage them.

The study also revealed that the 8 percent rate, which is the highest five-year compound growth rate, comes for the USA. Europe's growth was over 7 percent, and four percent from the Asia Pacific. Data sources came from P&I 1000, annual reports, websites, and from the pension fund organizations itself.

Chris Ford, the global head of investment at Towers Watson, said that "While liabilities have also ballooned, this still represents a significant increase in savings wealth. However there is a growing feeling that the investment industry, despite having grown assets, has not focused enough on the end beneficiaries' needs or on managing costs in the 'investment food chain'."

"Instead it has focussed on relative returns over total returns, and has allowed excessive risk to build up in portfolios at the same time as costs have increased to a level that is far higher than can be justified in aggregate," Ford added in his statement that appeared on Actuarial Post UK.

The study also showed that ten years ago, the total assets of the world's top pension funds increased 27% and has reached over $8 trillion. It was a significant increase from the previous high record of $6.6 trillion in 2003. Moreover the research also found out that 67% of the total assets came from the defined benefit (DB) funds. This was, however, lower from the recorded 75% five years ago.