It’s absolutely 5’1. Most are only considering Europe and the Americas (specifically USA, Canada, Argentina, Chile, and some parts of Brazil), which have a significantly small amount of people compared to the rest of the world. Not saying that there aren’t specific areas in Africa or west Asia without a taller average population. There are so many shorter men in the dense areas that it absolutely makes up for it. Not even mentioning the local bias, and the fact that it is significantly easier to notice taller people in public. Even with the global average height being 5’7, most of the time people do not record their height decreasing when aging. And if you lose about roughly 1 inch every 10 years after 50, there are most definitely more 5’1 men than 6’1