The narrative that you and Gates peddle relies on a poverty line of $1.90 per day. You are aware, I’m sure, that this line is arbitrary. Remarkably, it has no empirical grounding in terms of how much money is necessary to satisfy actual human needs. Indeed, the empirical evidence we do have demonstrates that $1.90 is far too low to be meaningful, for reasons I have outlined in my work (see here and here). See Reddy and Lahoti’s critique of the $1.90 methodology here.

Here are a few points to keep in mind. Using the $1.90 line shows that only 700 million people live in poverty. But note that the UN’s FAO says that 815 million people do not have enough calories to sustain even “minimal” human activity. 1.5 billion are food insecure, and do not have enough calories to sustain “normal” human activity. And 2.1 billion suffer from malnutrition. How can there be fewer poor people than hungry and malnourished people? If $1.90 is inadequate to achieve basic nutrition and sustain normal human activity, then it’s too low – period. It’s time for you and Gates to stop using it. Lifting people above this line doesn’t mean lifting them out of poverty, “extreme” or otherwise.

Remember: $1.90 is the equivalent of what that amount of money could buy in the US in 2011. The economist David Woodward once calculated that to live at this level (in an earlier base year) would be like 35 people trying to survive in Britain “on a single minimum wage, with no benefits of any kind, no gifts, borrowing, scavenging, begging or savings to draw on (since these are all included as ‘income’ in poverty calculations).” That goes beyond any definition of “extreme”. It is absurd. It is an insult to humanity.

In fact, even the World Bank has repeatedly stated that the line is too low to be used in any but the poorest countries, and should not be used to inform policy. In response to the Atkinson Report on Global Poverty, they created updated poverty lines for lower middle income ($3.20/day) and upper middle income ($5.50/day) countries. At those lines, some 2.4 billion people are in poverty today – more than three times higher than you would have people believe.

But even these metrics are not good enough. USDA data indicates that $5.04/day is necessary for achieving basic nutrition. Peter Edwards argues that people need about $7.40 if they are to achieve normal human life expectancy. The New Economics Foundation concludes that around $8 is necessary to reduce infant mortality by a meaningful margin. Lant Pritchett and Charles Kenny have argued that since the poverty line is based on purchasing power in the US, then it should be linked to the US poverty line – so around $15/day.

The literature on this issue is quite extensive – I have only scratched the surface here – and yet you proceed as if it doesn’t exist. That is intellectually irresponsible, and an inadequate approach to scholarship.

You say: “The level at which one sets an arbitrary cutoff like ‘the poverty line’ is irrelevant — the entire distribution has shifted, so the trend is the same wherever you set it.”

Not so fast. In fact, the story changes quite a bit. If we use $7.40 per day, we see a decline in the proportion of people living in poverty, but it’s not nearly as dramatic as your rosy narrative would have it. In 1981, 71% lived in poverty. Today it hovers at 58% (for 2013, the most recent data). Suddenly the grand story of progress seems tepid, mediocre, and – in a world that’s as fabulously rich as ours – obscene. There is nothing worth celebrating about a world where inequality is so extreme that 58% of people are in poverty, while a few dozen billionaires have more than all of their wealth combined.

A letter to Steven Pinker (and Bill Gates, for that matter) about global poverty

in both countries you can get a hot dog for $1 but the difference is in the first country the vendor will actually be prosecuted when the cheap slop makes you sick

(this is a joke, I'm sure you could get a quality hot dog for <$1 in China no worries)