N/A  (or None, 1980)
None
Nursery school
Kindergarten
1st grade
2nd grade
3rd grade
4th grade
5th grade
6th grade
7th grade
8th grade
9th grade
10th grade
11th grade
12th grade
1st year
2nd year
3rd year
4th year
5th year or more (40-50)
6th year or more (60,70)
7th year
8th year or more
Less than 1 year old
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90 (90+ in 1980 and 1990)
91
92
93
94
95
96
97
98
99
100 (100+ in 1970)
101
102
103
104
105
106
107
108
109
110
111
112 (112+ in the 1980 internal data)
113
114
115 (115+ in the 1990 internal data)
116
117
118
119
120
121
122
123
124
125
126
130