The report, published by the Boston Consulting Group, found that Switzerland is currently the largest offshore centre, with a 24% share - or $2.4trn (1.8trn, 2.1trn) in assets, twice as much as Singapore.

However, Switzerland's share of offshore wealth is projected to decline through 2021.

Meanwhile, offshore assets in Singapore and Hong Kong are likely to climb 8% and 6% respectively, because of their status as the preferred booking centers for regional clients and the anticipation of strong growth in Asia-Pacific, said BCG.

The growth in offshore wealth in Singapore and Hong Kong is primarily down to Asia-Pacific once again being the fastest-developing region, with nearly double-digit growth in global private wealth of 9.5%.

Investors in Asia-Pacific remained the largest source of global offshore wealth in 2016, with $2.9trn placed in offshore booking centres.

This is also helped by expansion of growth in China and India, expected to continue in the long term, but Chinas ongoing restrictions on investment outflows may slow it down to some degree in the short term.

BSG added that despite the expected merging of offshore and onshore margins, offshore bookings will remain a key growth opportunity, particularly in the upper high net worth and ultra high net worth market.

According to the report, global private financial wealth grew by 5.3% in 2016, to $166.5trn, driven by accelerating economic growth and the strong performance of equity markets in many parts of the world.

Western Europe posted modest growth (3.2%), which BSG said was linked to uncertainty over Brexit.

By the end of 2017, the level of private wealth in Asia-Pacific is projected to surpass that in Western Europe, and by 2019, the combined level of private wealth in Asia-Pacific and Japan is projected to surpass that in North America.

Meanwhile, Middle East and Africa rebounded strongly, with private wealth rising 8.5% to $8.1trn in 2016, with the richest country in the region, Saudi Arabia, posting moderate wealth expansion.

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Singapore, HK to outpace Switzerland for offshore wealth - International Adviser