This is the finding of a study by some Harvard guy reported here.

In the data, around 11 to 13 percent of the population was left-handed. And when broken down by gender — that is, comparing women to women and men to men — those lefties have annual earnings around 10 to 12 percent lower than those of righties, Goodman writes, which is equal to around a year of schooling. (That gap varied by survey and by gender, however.) Most of this gap can be attributed to “observed differences in cognitive skills and emotional or behavioral problems,” he writes, adding that since lefties tend to do more manual work than right-handers, the gap appears to be due to differences in cognitive abilities, not physical.

These problems only appear when the left-hander is the child of a right-handed mother. Like me.

Another study, reported in Wikipedia, came to a different conclusion:

In a 2006 U.S. study, researchers from Lafayette College and Johns Hopkins University concluded that there was no scientifically significant correlation between handedness and earnings for the general population, but among college-educated people, left-handers earned 10 to 15% more than their right-handed counterparts.

I am not smart enough to figure out why the two studies came up with different results..

The Vox article does throw us this bone:

Data has also shown that lefties, for example, are highly represented among high SAT-scorers and people with high IQs. What it may mean, Orszag notes, is that lefties are overrepresented in the intellectual stratosphere, but that for the population as a whole, it’s better to be a righty.

The “intellectual stratosphere” — I like that. On the other hand, there’s this, from Wikipedia:

There is a general tendency that the more violent a society is, the higher the proportion of left-handers.

There is presumably some advantage to being left-handed in hand-to-hand combat, because your opponent is less likely to have trained against people like you. (There’s a comparable effect in baseball, where left-handed batters are often helpless against left-handed pitchers, because they mostly face righties. This has led to the ultimate in baseball specialization, the southpaw who comes into the game in the late innings to face one critical left-handed batter, get him out, and then head for the showers.)

All in all, it’s a hard world for lefties. Now, in addition to being sinister, turns out we’re also cognitively impaired and doomed to earn less than our right-handed friends. Unless somehow we find ourselves in the intellectual stratosphere.