Real estate is an investment, an asset and a lifestyle — even for the world's wealthiest people, who own more than $3 trillion worth of owner-occupied residential property.

Sotheby's International Realty has just released a new report in conjunction with private wealth consultancy Wealth-X which reveals that the value of the homes and apartments lived in by the world's ultra-high net worth individuals exceeds the GDP of either France or the UK, and is double that of India. In 2014, there were 211,275 ultra-high net worth individuals, defined as those with $30 million or more in assets, around the world.

“We believe that a solid investment in real estate is one of the single best factors for building long-term wealth, and that many of today’s ultra high net worth consumers would agree," said Philip White, president and chief executive officer, Sotheby’s International Realty Affiliates LLC.

The report found that 79% of these super wealthy individuals own two or more properties and just over half of them own three or more residences. Ultra-high net worth individuals are increasing the number of properties they hold outside their home countries, and their favorite places to buy other homes are the United States, United Kingdom and Switzerland. The United States is the most popular country for foreign ultra-high net worth individuals looking for second homes, and New York is the city with the highest number of homes owned by these individuals. After New York, it's London, Hong Kong, Los Angeles and San Francisco.

"Besides the obvious need to own a property in one’s primary business location, the time spent in other locations, whether for leisure or business purposes, may make the ownership of a secondary residence a practical and financially responsible course of action," the report states.

Typically, residential real estate is particularly important for individuals with inherited wealth, the report states, but it found two particular groups of ultra-high net worth individuals bucking this trend: Chinese and Russian multiple homeowners who are self-made and young. "These two clusters are increasingly important buyers of luxury residential real estate around the world and spend a vast amount on such assets - for both personal and professional reasons," the report states. Outside of Russia, Russians' markets of choice are the United Kingdom, the United States, Italy, Austria, France and Switzerland, while for Chinese buyers, Hong Kong, Singapore and the United States are the main markets in which they purchase properties outside of China. Australia and Canada are also important markets for this group.