The average monthly pay for migrants at or below the age of 35 was just 2,513 yuan ($397) in 2011, according to a report issued Monday by the National Population and Family Planning Commission.

The figure represents a 29.4-percent increase from that of 2009, but is not nearly enough to cover housing and health care for migrants in light of the increasing cost of living, the annual report said.

For those who possess a bachelor's degree or greater among the group, the average monthly pay amounted to 4,608 yuan, the report said.

Conditions are also better for migrants in first-tier cities like Beijing and Shanghai, where the average monthly pay reached nearly 6,000 yuan, the report said.

The report said the total number of migrants reached 230 million last year, or 17 percent of the total population.

With an average age of 28, eighty percent of migrants are from rural areas and nearly 45 percent of them were born after 1980, the report said.

Younger migrant workers are more likely than their parents to engage in premarital relations, the report said, citing a premarital pregnancy rate of 42.7 percent among young migrants.