When population density is measured by standard methods, small countries and territories such as Macau, Monaco and Singapore rank among the world’s most crowded. However, given that mostly uninhabitable deserts cover more than 95% of Egypt and mudslide-prone mountains a quarter of Hong Kong, it is not surprising that the built-up urban areas in these places feel much more crowded than conventional comparisons suggest. So an alternative method of calculating population density is to divide the urban population by the area taken up by cities. On this measure Bangladesh’s urban areas hold about 75,000 people per square kilometre (194,250 per square mile). This is likely the world’s highest and is over 70 times the figure derived from cruder calculations. Since more than half the world’s population now lives in cities, a share the UN expects to rise to over two-thirds by 2050, adjusting population density to account for the smaller areas where people actually choose to live is probably a better way of gauging how crowded somewhere is.