The United Nations estimates that the world's population is over 55% urbanized (Link). When you dive deep into the statistics, you find they are messy: countries
Researchers using high-resolution satellite imagery estimate and a standard algorithm challenge this and instead estimate the world is over 84% urban already.
Out of curiosity, I checked my own district survey, which has the world's population broken out by provinces and districts. For each
All of the provinces together equate to about 6.9 billion people. (This is not the 2018 population, I know, but the important thing is the relative ratios.)
Provinces with population densities (population / total area) of more than 100 people per square kilometers (or 100 per 250
Provinces with population densities of more than 1,000 per square kilometer have a total population of 866 million. There are 330 such provinces. These are mostly cities. The most densely populated province in my database, right now, is Macau, with a density of over 57,000 per square kilometer.
Focusing on high-density populations can be a strategic way of penetrating a population, because people will naturally move to more-densely populated places (urbanized areas) for work, etc. And these figures seem to confirm that the world is generally even more urbanized, already, than the "floor" figure of 55%.