Just one percent of the world's population can call themselves millionaires or richer. But together they hold almost half the world's wealth, and their share is growing, according to a new study released Tuesday.

Some 18.5 million households around the world have at least $1 million worth of assets, for a total of $78.8 trillion - or about the same size as global annual economic output - Boston Consulting Group's annual report on global private wealth says.

That also amounts to 47 percent of total global wealth - based on holdings of cash, financial accounts, and equities, but not real estate - leaving the rest to be divided by the other 99 percent of the world's population. The elite one percent have steadily grown their share of global wealth from 45 percent in 2013 to 47 percent last year, the findings show, supporting worries among economists that inequality is growing around the globe.

The United States tops the world's count of millionaires by far, with eight million at least that wealthy, followed by China with two million millionaires and Japan with half that number. Per capita, however, the largest concentrations of wealthy are in the tax havens of Liechtenstein and Switzerland.