a diversity index allows us to calculate the probability that, if we select two people at random, we will find individuals who differ on the characteristic we are interested in. a score of 0 means everyone is the same and a score of 1 means everyone is unique. a score closer to 1 means that more people differ on whatever it is we are looking at. how does the diversity of household types (married couples, extended households, individual, single-parent, non–family group) compare between 1960 and 2015?