Table 1

Sample size of The National Survey on the Physical Growth and Development of Children in the Nine Cities of China (NSPGDC) I–V (1975–2015)

Age group	1975		1985		1995		2005		2015
Age group	Boys	Girls	Boys	Girls	Boys	Girls	Boys	Girls	Boys	Girls
Birth	2052	2001	1800	1800	1800	1800	1554	1512	2264	2147
1 month	1992	1940	1800	1800	1800	1800	1599	1573	1903	1896
2 months	1976	1901	1800	1800	1800	1794	1571	1559	1871	1856
3 months	2037	1985	1800	1800	1800	1795	1566	1588	1895	1893
4 months	2070	1938	1800	1800	1799	1800	1589	1581	1897	1852
5 months	2026	1994	1800	1800	1790	1788	1576	1580	1811	1841
6 months	2210	2202	1800	1800	1800	1800	1604	1585	1901	1884
8 months	2117	2090	1800	1800	1800	1793	1608	1622	1890	1881
10 months	2045	2072	1800	1800	1800	1794	1584	1581	1859	1862
12 months	2169	2053	1800	1800	1800	1800	1591	1594	1875	1870
15 months	2062	2029	1800	1800	1800	1800	1583	1579	1846	1886
18 months	2097	2029	1800	1800	1800	1800	1582	1572	1881	1869
21 months	2149	2083	1800	1800	1800	1800	1582	1573	1857	1815
2years	2387	2247	1800	1800	1800	1800	1581	1582	1909	1869
2.5years	2421	2286	1800	1800	1800	1800	1551	1561	1858	1878
3 years	2209	2190	1800	1800	1800	1800	1585	1601	1903	1908
3.5 years	2301	2238	1800	1800	1800	1800	1588	1600	1933	1924
4 years	2241	2202	1800	1799	1800	1800	1588	1602	1943	1866
4.5 years	2298	2244	1800	1800	1800	1800	1593	1599	1944	1895
5 years	2182	2237	1799	1780	1800	1800	1592	1595	1912	1892
5.5 years	2223	2151	1800	1800	1799	1800	1605	1597	1893	1908
6–7 years	2580	2540	1800	1799	1800	1800	1629	1623	1922	1924
Total	47 844	46 652	39 599	39 578	39 588	39 564	34 901	34 859	41 967	41 616