This post was updated at 1:00pm ET

Billionaires are getting richer, according to a new study from Oxfam. Gather together the wealth of the world’s richest people, and you now only need 80 of them before there’s enough in the pot to equal everything owned by the poorest 50% of the rest of the world combined. Back in 2010, you’d have needed 388 of the world’s richest to balance those scales.

The richest of the top 1%, the top billionaires on Forbes’ rich list, have seen their wealth accumulate faster over the last five years than even the rest of the super-rich, Oxfam said. In 2010, the richest 80 people in the world had a net wealth of $1.3 trillion. By last year, that was up to 1.9 trillion, an increase of $600 billion.

Together with the rest of the 1%, that group owned 48% of global wealth in 2014. That’s more uneven than in 2010, when they owned a little over 44%.

However, according to Oxfam’s data, we’ve been here before. Back in 2000, the 1% owned a higher percentage of global wealth than they do today. For a few years, the trend seemed to show that number falling, as the world’s poorest clawed some of it back. But in the past five years, that’s reversed.

Part of the problem, as identified by Oxfam, is that the rate of increase for the rich has speeded up, and it’s now so much higher than that for everyone else that it’s increasing the gap.

Critics have attacked Oxfam’s methodology. The charity uses data on net wealth—assets minus debts. Whether a deeply indebted American homeowner is poorer than a destitute African farmer is indeed a leap. Another charge is that adding up the wealth of the poorest people doesn’t make sense in the first place, because poor people are poor in different ways (few assets or debts) than rich people are rich (lots of assets and debts). Oxfam has defended the assumptions behind its “killer fact,” including how it’s much easier it is to count the wealth of the super-rich—there are only a handful of billionaires, after all, which is also Oxfam’s point.

The 1% has entered parlance, but who’s included? And do they constitute a problem or an asset?

Who are these people?

With a world population of 7.2 billion, there are around 72 million people in the top 1%—not all of whom are billionaires. In 2014, there were 1,645 people listed by Forbes as being billionaires, with Bill Gates back at the top after a year off. Of these, 90% are male, and 30% are American. And there’s evidence they’ve been running the show for a long, long time.

Is rising inequality inevitable?

Oxfam says not. In a campaign, the charity focuses on changes that could be made to the way global society is organized, including the eradication of extreme poverty and economic empowerment of women.

Why does it matter?

Economists like Dan Altman and Thomas Piketty argue that wealth inequality hampers growth and will only get worse in the future. Some have argued that it could be a good thing. And many have blamed it for misery, hopelessness and, ultimately, violence.

This post was updated to mention the debate and disagreement over Oxfam’s methodology.