Share of the population with basic numeracy skills by birth decade, 1500 to 1960

The shown estimates of basic numeracy are based on the share of people who stated their age correctly. The shown "ABCC-index" is based on the finding that in
population with lower numeracy skills "age heaping" occurs more frequently. "Age heaping" refers to the higher frequency of attractive numbers (i.e. rounded numbers
which are multiples of five), which occurs in populations with lower numeracy skills.