A society that exhibits cultural diversity has advantages that are quantitative as well as qualitative.
The quantitative advantage can been seen when studying cultures that have tried to stay isolated. In the United States, one of the most striking examples of the health risks of cultural isolation can be found in Amish communities. Because the Amish strive to keep their culture uniform and avoid cultural diversity, "founder effect" increases the chances of genetic abnormalities in Amish communities. The lack of cultural diversity can be literally a matter of life and death. The goal of Amish cultural isolation is to keep the culture strong by not diluting it, but the results of such isolation produce the opposite effect within the isolated community. Furthermore, since 10-20% of each generation of Amish leave their isolated communities, these genetic mutations and abnormalities do not solely affect the isolated culture. An advantage of cultural diversity can be quantitatively shown through the study of its converse, cultural isolation.
By definition, qualitative advantages are more difficult to prove, but one of the greatest advantages of cultural diversity can be found in the understanding that a greater pool of opinions, experiences, and cultures will produce solutions, innovations, and outcomes that benefit the greatest number of people. Being able to draw on multiple sources of art, government, craftsmanship, folklore, and history can provide new avenues of conflict mediation—a definite positive in a global society. Cultural diversity helps people focus on common needs and goals while acknowledging there could be multiple paths to the same end result. Cultural diversity can—interestingly enough—help people focus on what they have in common even while noting differences.
Both quantitatively and qualitatively, it is not an exaggeration to say the advantages of cultural diversity can affect the population in a positive way.