Table 2 Basic characteristics of participants in the NSPGDC III–V, 1995–2015.

Gender, n (%)

Male

42,915 (50.2)

37,560 (50.1)

44,550 (50.1)

0.904

Female

42,539 (49.8)

37,375 (49.9)

44,325 (49.9)

Region, n (%)

Northern

28,759 (33.7)

25,191 (33.6)

30,108 (33.9)

0.706

Central

28,686 (33.6)

25,248 (33.7)

29,873 (33.6)

Southern

28,009 (32.8)

24,496 (32.7)

28,894 (32.5)

Father education, n (%)

College degree and above

13,030 (15.2)

21,113 (28.2)

46,901 (52.8)

 < 0.001

Senior school/ technical secondary school

26,180 (30.6)

24,911 (33.2)

22,850 (25.7)

Junior middle school

40,587 (47.5)

26,420 (35.3)

17,691 (19.9)

Primary school and below

5594 (6.5)

2460 (3.3)

1327 (1.5)

Unknown

63 (0.1)

31 (0.0)

106 (0.1)

Mother education, n (%)

College degree and above

9439 (11.0)

17,978 (24.0)

45,758 (51.5)

 < 0.001

Senior school/technical secondary school

25,491 (29.8)

23,962 (32.0)

22,627 (25.5)

Junior middle school

42,704 (50.0)

29,223 (39.0)

18,836 (21.2)

Primary school and below

7751 (9.1)

3743 (5.0)

1538 (1.7)

Unknown

69 (0.1)

29 (0.0)

116 (0.1)

Family income, n (%)

 ≤ ￥30,000

–

52,061 (69.5)

6742 (7.6)

 < 0.001

￥30,000 ~ 49,999

–

10,292 (13.7)

21,505 (24.2)

￥50,000 ~ 99,999

–

6596 (8.8)

33,036 (37.2)

￥100,000 ~ 299,999

–

1139 (1.5)

23,504 (26.4)

 ≥ ￥300,000

–

107 (0.1)

3682 (4.1)

Unknown

–

4740 (6.3)

406 (0.5)

BW(g)^b,c

3300 (401)

3347 (414)

3357 (440)

 < 0.001

LAZ^b,d

− 0.06 (1.11)

0.31 (1.09)

0.37 (1.03)

 < 0.001

WAZ^b,e

0.13 (0.93)

0.37 (0.97)

0.41 (0.95)

 < 0.001

BMIZ^b,f

0.24 (0.95)

0.27 (0.99)

0.27 (0.98)

 < 0.001

HCZ^b,g

− 0.02 (0.96)

0.15 (1.01)

0.02 (0.98)

 < 0.001