Hello,
I am currently doing a panel data regression using fixed effects and have recently tumbled upon some past literature on the same topic in which they use age and age^2/100 as control variables, I was wondering why is this so (I understand age can be used as a control) but especially I am confused as why they use age^2/100, also considering that the value of age^2/100 will be less than the age variable.
Many thanks