The figure comes from this paper [1]. I gather they do estimates based on sampling, but no doubt the testing rates and accuracy vary a lot from country to coun

The figure comes from this paper [1]. I gather they do estimates based on sampling, but no doubt the testing rates and accuracy vary a lot from country to country, and the figure is presented for rhetorical impact over precision. [1] https://www.unicef.org/media/109361/file/The%20toxic%20truth.pdf https://www.unicef.org/media/109361/file/The%20toxic%20truth...