Today is Left Handers Day, a holiday to appreciate the untold millions of left-handers out there.
“Untold” because counting left-handers is very complicated. How do you assess whether people are left-handed? Do they write with their left hands? Or kick a soccer ball with their left foot? And what about the many countries in which you’d be hard-pressed to see a left-hander in action, due to cultural pressures to write and eat with the right hand? Is a brain scan of hemispheric activity required to confirm?
You see the problem.
To answer this question, a research team hailing from top universities in Greece, Germany, and the U.K. went big. They studied 2.4 million people through a series of meta-analyses of 262 data sets in 200 studies. They found that 9% to 18% of the population is left-handed, depending on how left-handedness is assessed.
And they found nearly as many mixed handers, who make up 9% of the population and have long been ignored in research.
Left-handedness is quirky, associated with higher drinking rates, older mothers, lower incomes, poor childhood development, and a few recent presidents. (George H. W. Bush, Bill Clinton, and Barack Obama were all lefties.)
The researchers say their meta-analysis is the “largest reported study to estimate the prevalence of left hand preference” to date. You can check out the full findings here.