Why did the use of african slaves increase in the americans during the 1500s

Mexican graveyards are the only evidence which connoted the existence of slavery in America in 16 century. The records which had the count of the slaves transported during the 16th century were less. But from seventeenth century, the records are available.

There was a massive depletion of population in Africa due to the export of slaves from Africa. In order to protect themselves from ruthless Europeans people started to keep them armed with lethal weapons  

There were huge internal conflicts in Africa which led to increase of warlords who failed to establish a free state. This caused enslavement of Africans.

1. state-issued photo ids. provide them for free for those who can't afford them.

2. the system we have seems to be working nearly perfectly. seems like about 31 cases per billion votes cast

3. the national policy for hiring new employees which requires proof of eligibility to work. there are something like 20 types of identification which can be used for this.