Dividing people up into groups- then assigning a separate value to each group.
All a matter of public policy.
At the federal level:
Except for:
Federal alcohol prohibition for adults age 18-20.
A federal requirement that 18 year old males register for selective service while 18 year old females opt out.
Charging people different access fees for National Parks lands- based on the age of the individual. We pay for these lands the same as we pay for the wars in Iraq & Afghanistan.
Making gay military spouses ineligible for military benefits.
At the state level:
The version of marijuana legalization now in place in WA & CO leaves prohibition in place for adults age 18-20.
Photo- Port Townsend scene