The analysis of population trends is important to political leaders, community leaders, and businesses

I think the analysis of population trends is very important for all: the political leaders, the community leaders, and businesses. As they work directly with problems related with the communities, a good way to know and understand the problems that affect them is by these analysis. As they show changes of population influenced by factors like natality, mortality, immigration and emigration. In other words, they are a good way to know your society and it's behaviour.

The political leader will know some factors that are important in different sectors of society.

The community leader can compare his community with others and point out problems that otherwise could be missed.

The business can understand the behaviour of the market addapting and taking important decisions.  

the revolution instituted a short-lived roman republic.

the answer to your question is:

strong-mayor system