The number of billionaires in the world is growing -- and so is their wealth

Everyone breathe a big sigh of relief: The world just added 6% more billionaires.

The collective wealth of the world's nearly 2,500 billionaires also grew — to a record $7.7 trillion in 2015 up from $7.3 trillion in 2014, according to Wealth X's latest annual census.

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Rich offspring helped drive the growth, with people who inherited at least part of their fortunes representing the fastest growing segment among billionaires, with growth of nearly 30% year over year.

"Wealth helps accumulate more wealth," David Barks of Wealth X said to the Wall Street Journal, explaining how the small group continues to get richer each year, regardless of market conditions.

Billionaires who are under 35

To be fair, it remains true that most billionaires are not heirs or heiresses. More than half — 56% — of billionaires are self-made, according to the Wealth X census.

But there are also a number of alarming trends in the data for those concerned about income inequality, especially with regards to gender: The wealth gap between men and women, for instance, persists even among the world's wealthiest people — and is growing.

The disparity between male and female billionaires grew between 2014 and 2015, from 8.1 men for every one woman, to 8.4 in the latest data. The percentage of billionaire wealth held by men also climbed, from 87.2% to 88.6%.

Income inequality more broadly has been a hot-button issue in the 2016 presidential campaign for both parties.

Most Americans did see wage growth in the last year, with the bottom 99% of incomes growing 3.9%, but incomes for the top 1% of earners still grew far faster, at 7.7%.

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Generally, income inequality in the United States has been on the rise for decades: In 2013, the amount of wealth held by the richest 1% of Americans reached the same level it was in 1928, when the richest 1% of Americans captured almost 24% of total income.

There's now solid evidence that current generations of Americans will actually be poorer than their parents: Between 30% and 40% of American workers may never see a pay raise again, according to a study published in July by the McKinsey Global Institute.

Alas, the disparity in earnings between the rich and poor (or middle class) is not without societal consequences.

We are also already seeing other effects of income inequality on social institutions like marriage. People in areas of high income inequality, for example, are more likely than those in areas of greater equality to have children before getting married, according to a recent study from Johns Hopkins University.