as a risk free rate, if T-bill is 18% which means US government is having big trouble. It is in finace distress, so It is just like a junk bond. BTW, at young age, probably no one will look at T-bill becasue you have decades to bear the risk. People invest in some bonds, but a lot of them are copoprate bond which has higher risk and higer return as well compared to T-bill.
