“Are billionaires feeling the pressure?” UBS Group and PwC ask in a new report.

The firms note that the tremendous wealth creation of the past three decades paused in 2015, as the population of billionaires in the 14 countries it studies grew by only 50, to 1,397, and total wealth fell from $5.4 trillion to $5.1 trillion. Average wealth dropped from $4 billion in 2014 to $3.7 billion last year.

Headwinds such as the transfer of assets within families, commodity price deflation and an appreciating U.S. dollar have affected the growth of billionaire wealth. Although it’s too early to know whether the past 30 years’ extraordinary wealth creation is coming to an end, it is clearly slowing, the report says.

Some 47 percent of billionaire wealth is based in the U.S., but the ultra-wealthy population there rose by only five new billionaires in 2015, and total billionaire wealth fell by 6 percent to $2.4 trillion, though newer money fared better than old.

Multigenerational billionaires’ ranks shrank by 16 percent, to $4.3 billion on average, while those of self-made billionaires fell by just 4 percent ($4.5 billion).

“The U.S. has always been a standout for creating wealth, and this report shows that the American dream is alive, with the wealth of the self-made billionaires outweighing that of the multigenerational billionaire,” John Matthews, head of ultra-high-net-worth at UBS Wealth Management Americas said.

Meanwhile, UBS and PwC’s data show that Asia minted a new billionaire every three days in 2015; China accounted for more than half of the total 113 additions. Total billionaire wealth in the region last year stood at $1.5 trillion, down slightly from 2014, largely because of currency depreciation.

There’s more to this picture, however. Far more Asian billionaires dropped off the database last year than in Europe or the U.S.: 80, compared with 44 and 36, respectively. Forty Chinese tycoons lost billionaire status as government scrutiny and asset price volatility undermined wealth.

Billionaire wealth often falters because of business risk and dilution from ineffective governance and inadequate succession planning. Of the fortunes that have fallen below the billion-dollar dollar mark since 1995, 70 percent was not preserved beyond the first generation and 20 percent beyond the and second, according to the report.

Europe, however, stands out as home of multigenerational billionaires, proving best at preserving wealth. The report says Europe’s old legacies provide a model Asia’s family-orientated billionaires may want to follow to preserve theirs.

The research shows that successful legacies tend to have a sensible and clear family governance/vision and maintain a stable business across generations. Europe’s billionaire families benefit from significant contributions to society and the economy. Old-wealth families have a common philosophy and understanding of their purpose and values that glues family members together and provides a common identity.

Wealth Transfer

UBS and PwC estimate that 460 billionaires will pass on $2.1 trillion to their heirs over the next two decades. For the younger Asian economies, where more than 85 percent of billionaires are first generation, this will be the first intergenerational wealth transfer.

What are the implications? According to the report, the new generation’s values are broader and choices greater. Millennials may choose personal careers over working in the family business, or philanthropy over entrepreneurialism. This is likely to influence the structure and type of legacies established. Many billionaires may cash out. Those who choose to keep their businesses have heirs who are increasingly likely to become owners, not managers.

After 35 years’ growth of wealth, billionaire philanthropy is expanding across the globe, with potentially significant benefits for society and the environment. New giving models—including impact investing, loans, contracts and guarantees—are coming to the fore, and millennial billionaires are putting philanthropy at the heart of their family values.

The report notes, however, that a strategy gap could limit the effectiveness of this generosity. Many donors struggle between following their passion and thinking strategically about its potential benefits. Many also have yet to adopt best practice in measurement.

In addition, few are willing to take the risks and adopt a longer-term view that the problems they seek to solve require. As well, many want to shape programs themselves, overlooking that the most complex problems can be solved only with cooperation and cross-sector approaches.