Some think the more diverse nationalities and cultures a country has, the more appealing and fast developing it becomes. Although, I think its true that the attractiveness of a country is dependant on the range of its traditions, I do believe that development of a country not only does not depend on how many nation it have, but also can be hurt by its diversion of cultures.
On the one hand, its clear that many think it is a country which has rich culture that is more interesting. Its, indeed, beneficial for tourism and economy. In my country, for example, most people choose countries to visit, which has traditions, nations and art as diverse as possible.Thus, our neighbours which have population that include multitude of nationalities and cultures have enjoyed booming industry of tourism. On top of that, youngsters can learn how to appropriately treat people from different cultural backgrounds from firsthand experience. So they will not have any problems in business when dealing with foreign businessmens.
On the other hand, big differences in a society can lead to misunderstandings and conflicts.
In the USA, for example, it was the difference of opinions about the future of the country that lead to civil war. If they had shared the same idea, world would not see those bloody battles. In addition, industry of Austria-Hungarian Empire had been suffocated by the nationalizm of three main nations of this country, and eventually this country was torn apart after WW1 becouse of differnces in population and a big debt.
In conclusion, while I belive it seems useful to have some diversion in the population of a country for its prosper, I think big differnces in society can trigger big conflicts.