I don't know how to solve this situation.

Population fluctuations greatly affect the economic situation.

The profits of this company increase and decrease every year.

His house is very big.

His opinion had a big influence on my decision.

That news greatly influenced his opinion.

The population of Japan is decreasing.

He is an expert in economics.

He is a 'big friend', an adult fan of that anime.

That decision had a bad effect on our project.