Final answer:
The stage at the end of the 30th year is unclear without context, but in demographic terms, Stage 4 reflects a stable population with low birth and death rates. The transition to Stage 4 from Stage 3 involves a decline in birth rates to match the low death rates, showing a stable society with slow or zero population growth.
Step-by-step explanation:
The stage at the end of the 30th year could be referring to the demographic stages in the context of the demographic transition model, where societies transition through different stages of population growth. However, without specific context, it's unclear which stage the question refers to, as it could also relate to different subjects such as developmental psychology or the stages of personal development. If we consider it in the context of the demographic transition model, the transition from Stage 3 to Stage 4 involves a shift towards a stabilization of population numbers.
In Stage 3, you would typically see a declining birth rate along with increased urbanization, while death rates continue to fall. In Stage 4, both the birth and death rates are low, leading to a stable and potentially declining overall population. Comparing this to Stage 3, for a society to shift to Stage 4, the birth rate would have to fall to match the already low death rate, suggesting a higher level of economic development, access to education, and widespread use of family planning.
The age structure diagram for Stage 4 would show an evenly distributed population across various age groups, indicating slow or zero population growth. This represents a population that is not rapidly growing, unlike the previous stages.