The assets of the world's wealthiest individuals are mostly tied up in public equities and privately held businesses, but a distinct slice of their wealth is in real estate — though the share has edged down when compared with last year, according to the latest Wealth-X Billionaire Census.

In 2017, according to the Billionaire Census, public holdings formed 41.5% of billionaire assets, while private holdings accounted for 33.3%. Liquid assets, that is cash or its equivalent, were 22.9%. A wealth category the census refers to as "real estate and luxury assets" totaled 2.3% of billionaire holdings.

In 2016, the share in real estate and luxury assets was 3%. That is about $80M in real estate and luxury asset holdings per billionaire.

The drop "largely reflected the shifting structure of billionaires’ broader portfolios, as luxury asset markets performed strongly," the report read, referring to the art, fine wine and jewelry sectors.

According to Wealth X, 173 billionaires' primary source of wealth is real estate, for a total of $468B in assets — meaning more billionaires owe their wealth to real estate than to manufacturing or tech. The average real estate billionaire worldwide is worth $2.7B, which is less than in finance and banking, industrial conglomerates or tech, but more than manufacturing billionaires.

"While changes to taxation and residency rules (and Brexit uncertainty in the UK) have contributed to a cooling in some high-end residential markets, developments in the property sector as a whole have remained positive from a wealth perspective, owing to a combination of robust housing demand (both from locals and investors), constrained supply and favorable financing conditions," the census said.

New York is the world’s top billionaire city, with 103 billionaires calling it home. Hong Kong is closing the gap, however, with 93 billionaires living in the country in 2017, up 21 billionaires since the previous year. The third-largest billionaire city is San Francisco, which has seen stronger growth in the number of billionaires living within the city than any U.S. city in recent years, reflecting prodigious wealth gains in the tech sector.

For the first time ever, there are more billionaires in Asia than North America, 784 compared with 727, because of the rapid expansion of wealth in both China and India. But North American billionaires still hold more total assets: about $3.2 trillion compared to $2.3 trillion.