Comment by falcor84

"A lot of people" never could do simple calculations, regardless of calculators. But if you're interested in actual figures over time, this data from nationsreportcard.gov would probably be the best longitudinal data source we have about the US, showing a strong general increase in mathematical scores, both for 9 and 13 year-olds, from when calculators started being introduced in the 70s and until the 2010s. Note that there's a recent decline over the last decade, partially explained by the pandemic, but even with it, current scores are higher than what they were in the 70s.

https://www.nationsreportcard.gov/ltt/mathematics/scores-per...

https://www.nationsreportcard.gov/ltt/mathematics/scores-per...