BEIJING, May 1 -- The Chinese Academy of Social Sciences (CASS), a government think tank, has revised down the country's annual agricultural output growth for 2007 to four percent compared to its January projection of five percent.The revision came two weeks after the National Bureau of Statistics released a lower-than-expected first quarter rise of 4.4 percent, underscoring a decline for three consecutive years from 6.3 percent in 2004 to last year's five percent.The percentage of gross domestic product generated by agriculture was also expected to decline from last year's 11.8 percent to less than 11 percent, said the CASS in its 2006-2007 Analysis and Forecast on China's Rural Economy, better known as the CASS Green Paper on China's Rural Economy.Zhang Xiaosha, director of the Rural Development Institute of the CASS, attributed the slower growth to rural labor outflow and accelerated urbanization and industrialization.With the vast rural population gradually absorbed by urban labor pool, the country's economic expansion would rely on more services and industrial production, he said.The Labor Science Research Institute affiliated to the Ministry of Labor and Social Securities has projected an aggregate inflow of 160 to 180 million rural laborers into cities from 2001 to 2010.Official figures reveal that the proportion of gross domestic product generated by the service industry has been growing the fastest from 29 percent in 2004 to nearly 40 percent last year. Industrial production held 48.7 percent of last year's domestic products, only a slight rise if compared with the previous 47.5 percent.China's gross domestic output grew up by 11.1 percent year-on-year to 5.03 trillion yuan in the first quarter, with the industrial output of agriculture standing at 363.1 billion yuan, up 4.4 percent year-on-year.