And the relevant paragraph regarding NYC: The standardized Entropy Index measures how close a total population is to sharing balanced percentages across its racial/ethnic groups. If one subgroup is 100 percent of the population, then the standardized index score will be 0. If the four racial/ethnic groups are each 25 percent of the population the score would be one. Houston has the highest entropy score of the 10 largest metropolitan areas, 0.874. New York is a close second with a score of 0.872. All but two of the 10 largest metropolitan areas, Boston and Philadelphia, have a higher entropy score than the national average of 0.709, meaning that in general the large metropolitan areas are more diverse than the nation as a whole.
EDIT: I'm not going to argue the pros or cons of the methodology because I'm not familiar with the field of study.