Answer:
4–10%, depending on region of the world
Explanation:
No individual has personal knowledge of the rates of left handedness among world population groups, so the best anyone can do is report the results of studies made by others.
In studies of rates of left handedness published over the past 55 years, the highest rates (about 10%) are reported in Western Europe, North America, Australia, and New Zealand.
The lowest rates, 4–6%, are reported in Asia, Africa, and South America.
The reasons for the differences are unknown. The rates are speculated to be affected by genetics, cultural norms related to conformity, or both. Rates tend to be higher where left-handedness is better tolerated.
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In my own experience, groups of people with high levels of certain skills (language, music, math, spatial) tend to have higher rates of left handedness than the 10% seen in the general population. There are some occupations where being left handed is a distinct advantage, so you'll find higher rates in those areas, too.
