Which factor affects the same percentage of a population regardless of the population’s density?

Flood

The factor which affects the same percentage of a population is Flood

A flood is an overflow of water on land which is usually dry. Sometimes a water resource such as river, lake or pond gets flushed with too much water and sometimes heavy rains cause floods and devastate the population. The same percentage of a population regardless of the population's density is affected by the flood no matter what is the density of the population.

explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.