Overall the demographic transition is characterized by two main trends. The first trend is a reduction of fertility to
replacement or below-replacement levels (~2.1). The second trend is a reduction of mortality that allows most individuals
in society to reach an advanced post-reproductive age (~80). Both trends are universally associated with socioeconomic
development (i.e. "modernization") and a transition from a pre-industrial to an industrialized economy. Reduced
fertility primarily results from the further extension of "childhood". However, it is probably more accurate to state
that reduced fertility results from continually delayed biological reproduction post-sexual maturation. The continued
trend towards delayed biological reproduction was again accompanied by a further intensification of parental investment,
and parents choosing to invest time and energy in the "quality" of offspring as opposed to the "quantity" of offspring.