At the other extreme, basic discoveries that immediately become
common property - the development of a new mathematical result
say - are human capital in the sense that they arise from resources allocated
to such discoveries that could instead have been used to produce current
consumption, but to most countries as well as to most individual agents they
appear 'exogenous' and would be better modelled as A(t) in section 2 than as
h,(t) in section 4.
h,(t) in section 4.