With approximately 1 million inhabitants, Cologne is the fourth largest city in Germany, and the largest in North Rhine-Westphalia. Over 2.1 million people live in the industrial region, which ... comprises the City of Leverkusen, the Erft District, the Rheinisch-Bergisch District, and the Upper Bergish District. In Cologne, the population density is around 2,380 people per km2, and in the entire region, 840 inhabitants per km2. Just under 20% of the total population of the City of Cologne are foreigners. There are a little over 500,000 households in the city, of which approximately half are single-person households; this trend is increasing.