文化差異
Cultural diversity is difficult to quantify, but a good indication is thought to be a count of the number of languages spoken in a region or in the world as a whole. By this measure, we may be going through a period of the precipitous decline in the world's cultural diversity. Research carried out in the 1990s by David Crystal (Honorary Professor of Linguistics at the University of Wales, Bangor) suggested that at that time, on average, one language was falling into disuse every two weeks. He calculated that if that rate of the language death were to continue, then by the year 2100, more than 90% of the languages currently spoken in the world will have gone extinct.