What country has the most left-handed people?
The countries which record the highest levels of left-handedness are those which are most tolerant of it - which means Europe, North America, Australia and New Zealand.
The rates are very low in Africa - but that is not surprising as using the left hand is culturally unacceptable. Having lived there, I was quickly advised always to use the right hand: offer someone food with your left hand, and you are indicating the hope that it poisons them. Rates are low in the Muslim world - because the left hand is deemed unclean: use it to clean your bottom, but never to eat, write, or touch your Koran. In China and Japan the ideographs used to write cannot easily be done using the left hand - stroke order and direction make a difference: children are encouraged to use the right hand from an early age as being left handed may hinder their education.
There does not appear to be any obvious genetic variation between different ethnic groups: social pressure is the main issue. Most people born left handed can learn to do things with the right hand if that is necessary to conform to their native culture.
While there is really no definitive answer for this, it looks as those countries that are more developed have a higher rate of left handedness. There are some countries that prohibit the use of the left hand for writing, etc. That used to be done here in the US as well, but people have since realized that a person using their left hand is not a demon, witch, etc and therefore we have a higher rate of left handedness.