Singapore - The ultra-wealthy are getting, well, ultra-wealthier.

While Singapore has minted just one more billionaire this year - adding to the list that stood at 26 last year - the total wealth of this exclusive club has increased 12 per cent from US$57 billion (S$71 billion) to US$64 billion.

Relative to population, only Luxembourg, Hong Kong and Switzerland have more billionaires than Singapore.

The census findings released by Wealth-X and UBS showed that Singapore has 5.1 billionaires per million people this year, compared to 4.9 per million last year.

The average Singapore billionaire is 64 years old and has a wealth of US$2.4 billion, enough to buy 5,000 four-room Housing Board flats.

He belongs to a men's club, with only one woman in the ranks. He's likely to hold a bachelor's degree and quite likely to say he's a self-made man.

Click here to see the billionaires in Singapore.

A Credit Suisse report last month showed that Singapore was home to 174,000 millionaires. But income inequality has been an issue - with the Gini coefficient rising - even though Credit Suisse said that the average Singaporean's wealth had gone up 6.8 per cent in a year to US$282,000 (including the worth of his home, if he owned it).

Explaining the increase in billionaires' wealth, Bank of America Merrill Lynch's Dr Chua Hak Bin said they could have amassed more money through investments.

"Properties and stocks have done well in a number of places, including the US, Australia and parts of Europe. They would have diversified globally," he said.

Click here to see the billionaires in Singapore.

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