The city of Quanzhou today is situated within a six-county prefectural-level administrative district with a population of approximately six million. This includes a municipal core with a population of around one half million; within this is the city proper (also known as Licheng) which includes the Old City, a densely built 7-square-kilometer district with between 160,000 and 200,000 inhabitants. Confusion over population numbers is due largely to high rates of migration. Officials estimate that in 1993 the "floating population" of unregistered or "temporary" migrants from elsewhere added another 800,000 people to the six county region (an additional 13%) and 40-50,000 to the population of the old city. The migrants who comprise the floating population are drawn by the rapid expansion of the city's economy, driven in large part by commercial investment of overseas Chinese capital.