The US has been identified as the best market for fund investors, whilst South Africa has been rated as the worst, according to a new study by investment researcher Morningstar.

Morningstar's Global Fund Investor Experience report assesses the experiences of mutual fund investors in 24 countries across North America, Europe, Asia and Africa and is based on criteria including investor protection, transparency, fees, taxation and investment distribution.

Each country was assigned a letter grade for each category, which was then used to produce an overall country grade. The report’s authors gathered information from available public data and from Morningstar analysts.

The US was the highest-scoring country, and received the top grade of A.

"The US is not a leader on regulation and taxation, earning only a middling score for that section, but US disclosure is clearly the world’s best, US fund expenses are the world’s lowest, and the country’s media do a fine job of emphasizing a long-term perspective and low costs," the report said.

Almost all European countries landed in the B- or C+ range, with only small differences occurring between markets.

At the bottom was Japan with a C, Hong Kong and New Zealand with C- grades, and South Africa with a D. South Africa's grade was primarily a result of its poor disclosure practices.

The UK earned a B- grade in the report, improving on its 2011 grade of C+. This was largely due to the dominance of open-architecture distribution in the market, giving most fund investors a wide array of choice.

New Zealand showed the largest improvement from the 2011 study, rising from a D- to a C-, because of positive regulatory changes and improvements in disclosure requirements.

The survey also found that bans on advisor commissions are spreading throughout the world. On top of the UK, which has already brought in a ban with the Retail Distribution Review, similar moves are underway in Australia and the Netherlands.