The demographic transition model describes 4 stages. Bolivia is in stage two (see the graph attached), at which birth rates still high but death rates are beginning to decrease.
Traditional demographic dynamics (stage 1) are characterized by high fertility and mortality rates and almost no growth in absolut population figures. Moreover, there are so-called 'checks', which are sharp and sudden mortality crisis such as wars, epydemies or starvation due to bad crops. This has been the reality until the industrial revolution all over the world, as production systems were mainly limited to agricultural activities, where crops were grown with very rudimentary technologies and only intended for survival.
There is a point in which the country or territory experiences transition to stage 2, due to economic progress and to the introduction of industrial and trade economic activities. At first, mortality rates decrease quickly because there are no more 'checks', no more mortality crisis due to starvation or epydemies. Right after, infant mortality will be the next to be reduced. Until mortality rates are not lower, fertility rates will remain high and when this happens it will trigger transition to Stage 3.