“The bottom half of the world’s population owns the same as the richest 85 people in the world.”

The stat was quoted last month in a report by the development organization Oxfam, but similar claims have mon.You’ve probably seen this statistic—or one like it—before in articles about economic inequality and assumed they must be somewhat true.

But they aren’t. In reality, they pletely meaningless.

One of the problems is that parisons are based on net worth (assets minus liabilities). If you aggregate all the people who have a negative net worth into one category and call them the “bottom half” then e up with some peculiar conclusions. As Felix Salmon says, “My niece, who just got her first 50 cents in pocket money, has more money than the poorest 2 billion people in the bined.”

But that “bottom half” (over 2 billion people) would include people like Eike Batista. Although he was the world’s eighth-richest person in March 2012, he now has a negative net worth of hundreds of millions of dollars. That puts him in the same category as people who live on less than a dollar a day. Is Salmon’s niece (or your own child) “richer” than Batista? Not in way we usually think of wealth: as the ability (or potential ability) to consume goods and services.

Salmon explains why such statistics are useless and misleading:

The first lesson of this story is that it’s very easy, and rather misleading, to construct any statistic along the lines of “the top X people have the same amount of wealth as the bottom Y people”.

The second lesson of this story is broader: that when you’re talking about poor people, aggregating wealth is a silly and ultimately pointless exercise. Some poor people have modest savings; some poor people are deeply in debt; some poor people have nothing at all. (Also, some rich people are deeply in debt, which helps to throw off the statistics.) By lumping them all together and aggregating all those positive and negative ledger balances, you arrive at a number which is inevitably going to be low, but which is also largely meaningless. The Chinese tend to have large personal savings as a percentage of household e, but that doesn’t make them richer than Americans who have negative household savings — not in the way that monly understand the terms “rich” and “poor”. Wealth, and net worth, are useful metrics when you’re talking about the rich. But they tend to conceal more than they reveal when you’re talking about the poor.