In the situations presented, what happens to the population and living standards is that they improve significantly avoiding a Malthusian catastrophe.
Malthusianism is a sociological concept that refers to the theory developed by Thomas Malthus in which he states that population growth at the rate that is being done will result in a decrease in resources for life, that is what he defined as Malthusian catastrophe.
According to the above, the situations presented would be a way of delaying the Malthusian catastrophe because if people marry late, the probability of having children is reduced for biological reasons. In addition, the number of children is going to be reduced.
On the other hand, if an earthquake occurs that destroys half the world and kills half the population, the Malthusian catastrophe is delayed because the available resources would increase in relation to the existing population.
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