The world’s ultra-wealthy population rose sharply in 2017, thanks to the auspicious global economic climate, robust asset markets, and relatively stable exchange rates against the U.S. dollars running through the year. Hong Kong, meanwhile, saw its ultra-high-net-worth population surpass New York for the first time.

The world’s ultra-high-net-worth (UHNW) population—those with a net worth of US$30 million or more—increased 12.9% to 255,810 last year, following a moderate growth of 3.5% in 2016. Their combined wealth, meanwhile,...