Census
World population estimates

The earliest estimate of the world population was made by Giovanni Battista Riccioli in 1661; the next by Johann Peter Süssmilch in 1741, revised in 1762; the third by Karl Friedrich Wilhelm Dieterici in 1859.

In 1931, Walter Willcox published a table in his book, International Migrations: Volume II Interpretations, that estimated the 1929 world population to be roughly 1.8 billion.
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