In 2017, the total economic output of the four first-tier cities of Beijing, Shanghai, Guangzhou and Shenzhen (BSGS) reached over 10 trillion yuan, accounting for 12.3% of China's total GDP, down from 12.5% of 2016. Judging from the data held by ANBOUND, during the period2007-2017, the total economic output of BSGS, which was kept at about 12.5% of the national GDP, accounted for the 1/8 of national GDP.Among them, the total economic output of the four first-tier cities of BSGS in 2007 accounted for the highest proportion of the total national GDP in 2007, reaching 13.4%. In 2012, the total economic output of the four first-tier cities of BSGS accounted for the lowest proportion of the total national GDP, which was 11.9%. Looking from the trend, the ratio of the four first-tier cities' total economic output to the total national GDP in 2007-2012 has been declining. However, from 2012 to 2016, the ratio of the four first-tier cities' economic output to the total national GDP has been on the rise. However, although BSGS's share in total national GDP declined in 2017, it is still higher than that in 2012-2015. After preliminary calculation, in 2017, Beijing achieved a GDP of 2.80004 trillion yuan, an increase of 6.7% over the previous year at a comparable price, and a deceleration of 0.1 percentage point from the previous year. Shanghai realized a GDP of 3.013386 trillion yuan, an increase of 6.9% over the previous year at a rate of comparable prices, the growth rate unchanged from the previous year; Guangzhou is expected to have a full-year GDP of 2.15 trillion yuan, an increase of over 7% over the previous year; and Shenzhen is expected to have a total GDP of more than 2.2 trillion yuan in 2017 , An increase of about 8.8% over the same period of last year.