Beijing -- Su Ren always wondered where he would live after finishing college, but he never considered Inner Mongolia.

Now, because Chinese authorities' want to transfer skilled workers from the country's booming cities to underdeveloped provinces in its "wild west," Su and thousands of students like him are experiencing a velvet-gloved version of China's Maoist past -- the forced migration of workers.

"They told me to come to a meeting in the afternoon," Su says, recounting a phone call he received from the Beijing Institute of Technology's recruitment office last June.

"When I went, there were about 80 of us. They told us that if we did not get jobs by June 30, we would have our papers sent to Inner Mongolia," says Su, 21, who was about to graduate in engineering from the elite university. "They didn't ask us if we wanted to go, they didn't ask us anything. My whole life was turned upside down."

The "papers" Su referred to are his hukou, or residence permit, and dang an, or personal file. Together they are "China's most insidious tools of social control," says Duan Chen Rong, a professor of demographics at the People's University in Beijing.

A hukou is a residence permit issued to every citizen. It determines where a person can live. "It is like a passport for travel within China," says Duan. The difference is that it is a restricted passport that prevents holders from moving freely within the country.

Issued at birth by local governments, a hukou used to require a person to reside only within the town or district of his or her birth. Since 1984, a loosening in rules has made it easier for people to move between towns, but it is still difficult for an average person with a rural hukou to get permission to move to a large city like Beijing. Su, who had a hukou from Xinjiang, a poor province in western China, was one of relatively few students who beat the odds by getting into the prestigious BIT.

The dang an is an even more Orwellian creation of the Maoist years. Essentially a personal file that the government maintains on every urban citizen, a dang an records people's entire lives, including details on what they studied, what grades they received, what work they did, how they performed, what organizations they belong to and anything they did that might be deemed politically incorrect.

"A person's dang an is created when they enter primary school and maintained until death," says Duan.

During the Maoist era from 1949 to 1976, both the hukou and dang an controlled the course of a person's life -- where they lived, the education they received, which jobs they were allowed to do, even the quality of medical care they were entitled to receive.

During the past two decades, reforms have made the hukou and dang an less intrusive. Some provinces have virtually stopped using them altogether. But in many other places, they are very much alive. Su says that at his university, authorities are using the system to inflate the employment rate among graduates and thus make themselves look better.

"If we don't get a job, the dang an is supposed to stay with the university or be sent back to our hometown," Su explains. "So if my dang an is sent to Inner Mongolia, on paper it will look like I have left university for a job there."

Though China's dramatic economic growth of the last two decades has raised hundreds of millions out of poverty, the country's market-oriented reforms have created serious inequalities, between urban and rural areas, and between the relatively wealthy east and the more impoverished and landlocked western provinces.

"China has pursued an economic strategy that has favored the urban industrial sector while exploiting the farm sector," says Kam Wing Chan, a professor of geography at the University of Washington who has studied China's hukou policy for several years. "In small towns and even some medium-sized cities, there are few, if any, benefits attached to the local hukou.

"Having a city hukou is like having EU (European Union) citizenship. Having a rural one is like being a citizen of a Third World country," says Julio Arias, an investment consultant. Such perceptions are creating a "problem of demand and supply," says Duan of the People's University. "The government needs skilled workers to develop backward provinces, but skilled people don't want to go there. That is why every year there are some students with specific skills who have to be sent there." Duan says that in the past, small numbers of students were sent off to "backward" areas, such as Inner Mongolia, because of the situation this year, thousands of students are being told to relocate.

For Su and his family, who had to struggle to afford the $5,000 cost of his education, this has meant there is no cause to celebrate his graduation. Convinced that having his papers sent out of Beijing will deny him the chance to improve his life, Su says he will stay in the city illegally and work as a salesman on commission for a small motor manufacturerThis will make him one of the city's estimated 3 million illegal migrants and will be deprived of all social benefits and excluded from prime employment opportunities.

It is a bleak future, but one he prefers to forced relocation to Inner Mongolia.

"My family was already forced to move once. In 1962 they had to go to Xinjiang because of a famine in Henan. Life there was tough," says Su. "I really wanted a career in Beijing so I could earn enough to take care of my family."