A decades-old system that divides China's population into two categories, rural and non-rural, is under scrutiny by a new study, state media reported. The hukou system was established in the 1950s to control population migration. But, as more rural workers continue to gravitate towards the cities where even the most menial jobs can pay much more than what may be earned in rural areas, the system is becoming strained. The study by Beijing's Renmin University found the city's "floating population" to number some 3.57 million people, most of whom stay in the city almost five years. What's more, about 41% of them bring their entire families. But under the hukou policy they are not given social security, education, medical care, or housing assistance. Zhang Chewei, vice-president of the Research Insitute of Population Science at the Chinese Academy of Social Sciences, said the system needs work and "hinders market development in both rural and urban areas."