Japanese schoolchildren have been measured every April since 1900. The record shows 12.8 cm of growth, eight years the war erased, and a plateau that has now lasted more than twenty years.
+12.8centimetres gained by the average seventeen-year-old boy between 1900 and 2015girls gained 10.9 cm · the war cost 1.9 cm between 1939 and 1948 · nothing has been gained since 1994
Japanese seventeen-year-old boys gained 12.8 cm between 1900 and 2015. Girls gained 10.9 cm. Then both stopped.
Every April since 1900, Japanese schools have measured their pupils and sent the figures to the ministry. The result is one of the longest continuous records of human growth anywhere: 107 years of mean height and weight, for thirteen ages, for both sexes.
It is not a smooth curve. It has a hole in it where the war was, a fall on the far side of that hole, four decades of the fastest growth the record has ever seen, and then a flat line that has now run for more than twenty years.
02
The whole record
Two gaps, one fall, one surge, one plateau — the shape of the century is visible in a single line.
The shaded bands are years nobody measured. The lines stop at their edges rather than crossing them, because a line drawn across 1940–1947 would invent eight years of growth that nobody recorded, and would hide the only sustained fall in the entire series.
Switch the measure to weight or leg length, and the age to any of the thirteen the survey publishes. The vertical scale refits to whichever age you choose — a five-year-old and a seventeen-year-old are sixty centimetres apart, and one scale for both would flatten everything worth seeing.
Mean height, weight and leg length, 1900–2015
Japanese schoolchildren, by age and sex. Shaded years were not surveyed.
Height · Age 17 (upper secondary) · 1900–2015 · highest 170.9 cm
Boys
Girls
no survey
Table · Height · Age 5 (kindergarten)
Table · Height · Age 5 (kindergarten)
Measure
Value
Boys · 1948
103.7 cm
Boys · 2015
110.4 cm
Boys · change over the record
+6.7 cm
Boys · highest
111.0 cm (1995)
Girls · 1948
102.5 cm
Girls · 2015
109.4 cm
Girls · change over the record
+6.9 cm
Girls · highest
110.1 cm (1988, 1990, 1995, 1996)
Boys
Girls
no survey
Table · Height · Age 6 (elementary)
Table · Height · Age 6 (elementary)
Measure
Value
Boys · 1900
107.0 cm
Boys · 2015
116.5 cm
Boys · change over the record
+9.5 cm
Boys · highest
116.8 cm (1990, 1991, 1992, 1993, 1994, 1995, 1998, 2004)
Boys · 1939 to 1948
109.1 cm → 108.1 cm (−1.0 cm)
Girls · 1900
104.8 cm
Girls · 2015
115.5 cm
Girls · change over the record
+10.7 cm
Girls · highest
116.1 cm (1991, 1994)
Girls · 1939 to 1948
108.1 cm → 107.3 cm (−0.8 cm)
Boys
Girls
no survey
Table · Height · Age 7 (elementary)
Table · Height · Age 7 (elementary)
Measure
Value
Boys · 1900
110.9 cm
Boys · 2015
122.5 cm
Boys · change over the record
+11.6 cm
Boys · highest
122.7 cm (1994)
Boys · 1939 to 1948
113.9 cm → 112.1 cm (−1.8 cm)
Girls · 1900
110.0 cm
Girls · 2015
121.5 cm
Girls · change over the record
+11.5 cm
Girls · highest
121.8 cm (1989, 1990, 1994, 1995, 2002)
Girls · 1939 to 1948
112.9 cm → 111.9 cm (−1.0 cm)
Boys
Girls
no survey
Table · Height · Age 8 (elementary)
Table · Height · Age 8 (elementary)
Measure
Value
Boys · 1900
116.1 cm
Boys · 2015
128.1 cm
Boys · change over the record
+12.0 cm
Boys · highest
128.3 cm (1997, 2006, 2007, 2009)
Boys · 1939 to 1948
119.3 cm → 117.4 cm (−1.9 cm)
Girls · 1900
113.9 cm
Girls · 2015
127.3 cm
Girls · change over the record
+13.4 cm
Girls · highest
127.6 cm (1994, 1995, 1996, 1997)
Girls · 1939 to 1948
117.7 cm → 116.4 cm (−1.3 cm)
Boys
Girls
no survey
Table · Height · Age 9 (elementary)
Table · Height · Age 9 (elementary)
Measure
Value
Boys · 1900
120.0 cm
Boys · 2015
133.5 cm
Boys · change over the record
+13.5 cm
Boys · highest
133.7 cm (2003, 2008)
Boys · 1939 to 1948
125.0 cm → 121.9 cm (−3.1 cm)
Girls · 1900
119.1 cm
Girls · 2015
133.4 cm
Girls · change over the record
+14.3 cm
Girls · highest
133.6 cm (1997, 2008, 2013)
Girls · 1939 to 1948
123.1 cm → 121.1 cm (−2.0 cm)
Boys
Girls
no survey
Table · Height · Age 10 (elementary)
Table · Height · Age 10 (elementary)
Measure
Value
Boys · 1900
123.9 cm
Boys · 2015
138.9 cm
Boys · change over the record
+15.0 cm
Boys · highest
139.1 cm (1998, 1999, 2000)
Boys · 1939 to 1948
128.2 cm → 126.1 cm (−2.1 cm)
Girls · 1900
123.9 cm
Girls · 2015
140.1 cm
Girls · change over the record
+16.2 cm
Girls · highest
140.4 cm (1998)
Girls · 1939 to 1948
127.7 cm → 125.7 cm (−2.0 cm)
Boys
Girls
no survey
Table · Height · Age 11 (elementary)
Table · Height · Age 11 (elementary)
Measure
Value
Boys · 1900
127.9 cm
Boys · 2015
145.2 cm
Boys · change over the record
+17.3 cm
Boys · highest
145.3 cm (1998, 1999, 2000, 2001, 2008)
Boys · 1939 to 1948
132.9 cm → 130.4 cm (−2.5 cm)
Girls · 1900
127.9 cm
Girls · 2015
146.7 cm
Girls · change over the record
+18.8 cm
Girls · highest
147.1 cm (1999, 2000, 2001, 2003)
Girls · 1939 to 1948
132.7 cm → 130.8 cm (−1.9 cm)
Boys
Girls
no survey
Table · Height · Age 12 (lower secondary)
Table · Height · Age 12 (lower secondary)
Measure
Value
Boys · 1900
133.9 cm
Boys · 2015
152.6 cm
Boys · change over the record
+18.7 cm
Boys · highest
152.9 cm (2000, 2001)
Boys · 1939 to 1948
137.8 cm → 135.0 cm (−2.8 cm)
Girls · 1900
133.0 cm
Girls · 2015
151.8 cm
Girls · change over the record
+18.8 cm
Girls · highest
152.2 cm (1999, 2001)
Girls · 1939 to 1948
138.8 cm → 136.1 cm (−2.7 cm)
Boys
Girls
no survey
Table · Height · Age 13 (lower secondary)
Table · Height · Age 13 (lower secondary)
Measure
Value
Boys · 1900
140.0 cm
Boys · 2015
159.8 cm
Boys · change over the record
+19.8 cm
Boys · highest
160.2 cm (2001, 2002)
Boys · 1939 to 1948
144.0 cm → 139.8 cm (−4.2 cm)
Girls · 1900
137.9 cm
Girls · 2015
154.9 cm
Girls · change over the record
+17.0 cm
Girls · highest
155.3 cm (1998)
Girls · 1939 to 1948
144.0 cm → 141.1 cm (−2.9 cm)
Boys
Girls
no survey
Table · Height · Age 14 (lower secondary)
Table · Height · Age 14 (lower secondary)
Measure
Value
Boys · 1900
147.0 cm
Boys · 2015
165.1 cm
Boys · change over the record
+18.1 cm
Boys · highest
165.5 cm (1999, 2000, 2001, 2002)
Boys · 1939 to 1948
152.1 cm → 146.0 cm (−6.1 cm)
Girls · 1900
143.0 cm
Girls · 2015
156.5 cm
Girls · change over the record
+13.5 cm
Girls · highest
156.8 cm (1997, 1998, 2000, 2001, 2005)
Girls · 1939 to 1948
148.7 cm → 145.6 cm (−3.1 cm)
Boys
Girls
no survey
Table · Height · Age 15 (upper secondary)
Table · Height · Age 15 (upper secondary)
Measure
Value
Boys · 1900
152.1 cm
Boys · 2015
168.3 cm
Boys · change over the record
+16.2 cm
Boys · highest
168.6 cm (2000, 2001, 2003)
Boys · 1939 to 1948
158.1 cm → 152.7 cm (−5.4 cm)
Girls · 1900
144.8 cm
Girls · 2015
157.1 cm
Girls · change over the record
+12.3 cm
Girls · highest
157.4 cm (1996, 1997, 1998)
Girls · 1939 to 1948
150.7 cm → 149.1 cm (−1.6 cm)
Boys
Girls
no survey
Table · Height · Age 16 (upper secondary)
Table · Height · Age 16 (upper secondary)
Measure
Value
Boys · 1900
156.1 cm
Boys · 2015
169.8 cm
Boys · change over the record
+13.7 cm
Boys · highest
170.2 cm (1998, 1999)
Boys · 1939 to 1948
160.9 cm → 157.9 cm (−3.0 cm)
Girls · 1900
146.1 cm
Girls · 2015
157.6 cm
Girls · change over the record
+11.5 cm
Girls · highest
157.9 cm (1996, 1997, 1998)
Girls · 1939 to 1948
152.1 cm → 151.3 cm (−0.8 cm)
Boys
Girls
no survey
Table · Height · Age 17 (upper secondary)
Table · Height · Age 17 (upper secondary)
Measure
Value
Boys · 1900
157.9 cm
Boys · 2015
170.7 cm
Boys · change over the record
+12.8 cm
Boys · highest
170.9 cm (1994, 1996, 1997, 1998, 1999, 2001, 2006)
Boys · 1939 to 1948
162.5 cm → 160.6 cm (−1.9 cm)
Girls · 1900
147.0 cm
Girls · 2015
157.9 cm
Girls · change over the record
+10.9 cm
Girls · highest
158.1 cm (1994, 1996, 1998, 1999, 2000)
Girls · 1939 to 1948
152.5 cm → 152.1 cm (−0.4 cm)
Boys
Girls
no survey
Table · Weight · Age 5 (kindergarten)
Table · Weight · Age 5 (kindergarten)
Measure
Value
Boys · 1948
17.5 kg
Boys · 2015
18.9 kg
Boys · change over the record
+1.4 kg
Boys · highest
19.4 kg (1993, 1995)
Girls · 1948
16.8 kg
Girls · 2015
18.5 kg
Girls · change over the record
+1.7 kg
Girls · highest
19.0 kg (1990, 1992, 1993, 1995, 1996)
Boys
Girls
no survey
Table · Weight · Age 6 (elementary)
Table · Weight · Age 6 (elementary)
Measure
Value
Boys · 1900
17.0 kg
Boys · 2015
21.3 kg
Boys · change over the record
+4.3 kg
Boys · highest
21.8 kg (1996, 2000)
Boys · 1939 to 1948
18.5 kg → 18.4 kg (−0.1 kg)
Girls · 1900
17.0 kg
Girls · 2015
20.8 kg
Girls · change over the record
+3.8 kg
Girls · highest
21.3 kg (1995, 1996, 1998, 1999, 2000)
Girls · 1939 to 1948
17.7 kg → 17.9 kg (+0.2 kg)
Boys
Girls
no survey
Table · Weight · Age 7 (elementary)
Table · Weight · Age 7 (elementary)
Measure
Value
Boys · 1900
20.0 kg
Boys · 2015
23.9 kg
Boys · change over the record
+3.9 kg
Boys · highest
24.5 kg (1997)
Boys · 1939 to 1948
20.3 kg → 20.1 kg (−0.2 kg)
Girls · 1900
19.0 kg
Girls · 2015
23.4 kg
Girls · change over the record
+4.4 kg
Girls · highest
23.9 kg (1995, 1996)
Girls · 1939 to 1948
19.4 kg → 19.5 kg (+0.1 kg)
Boys
Girls
no survey
Table · Weight · Age 8 (elementary)
Table · Weight · Age 8 (elementary)
Measure
Value
Boys · 1900
21.0 kg
Boys · 2015
26.9 kg
Boys · change over the record
+5.9 kg
Boys · highest
27.8 kg (2003)
Boys · 1939 to 1948
22.5 kg → 22.0 kg (−0.5 kg)
Girls · 1900
20.0 kg
Girls · 2015
26.4 kg
Girls · change over the record
+6.4 kg
Girls · highest
27.1 kg (1996)
Girls · 1939 to 1948
21.7 kg → 21.3 kg (−0.4 kg)
Boys
Girls
no survey
Table · Weight · Age 9 (elementary)
Table · Weight · Age 9 (elementary)
Measure
Value
Boys · 1900
23.0 kg
Boys · 2015
30.4 kg
Boys · change over the record
+7.4 kg
Boys · highest
31.3 kg (1998, 2003)
Boys · 1939 to 1948
24.6 kg → 24.0 kg (−0.6 kg)
Girls · 1900
22.0 kg
Girls · 2015
29.7 kg
Girls · change over the record
+7.7 kg
Girls · highest
30.7 kg (1999, 2000)
Girls · 1939 to 1948
23.7 kg → 23.4 kg (−0.3 kg)
Boys
Girls
no survey
Table · Weight · Age 10 (elementary)
Table · Weight · Age 10 (elementary)
Measure
Value
Boys · 1900
25.0 kg
Boys · 2015
34.0 kg
Boys · change over the record
+9.0 kg
Boys · highest
35.1 kg (1999, 2000)
Boys · 1939 to 1948
26.9 kg → 26.0 kg (−0.9 kg)
Girls · 1900
25.0 kg
Girls · 2015
33.9 kg
Girls · change over the record
+8.9 kg
Girls · highest
35.0 kg (1998)
Girls · 1939 to 1948
26.5 kg → 25.6 kg (−0.9 kg)
Boys
Girls
no survey
Table · Weight · Age 11 (elementary)
Table · Weight · Age 11 (elementary)
Measure
Value
Boys · 1900
27.0 kg
Boys · 2015
38.2 kg
Boys · change over the record
+11.2 kg
Boys · highest
39.5 kg (2001)
Boys · 1939 to 1948
29.3 kg → 28.2 kg (−1.1 kg)
Girls · 1900
27.0 kg
Girls · 2015
38.8 kg
Girls · change over the record
+11.8 kg
Girls · highest
40.1 kg (1998, 2000, 2001)
Girls · 1939 to 1948
29.5 kg → 28.2 kg (−1.3 kg)
Boys
Girls
no survey
Table · Weight · Age 12 (lower secondary)
Table · Weight · Age 12 (lower secondary)
Measure
Value
Boys · 1900
29.0 kg
Boys · 2015
43.9 kg
Boys · change over the record
+14.9 kg
Boys · highest
45.4 kg (2000, 2001)
Boys · 1939 to 1948
32.5 kg → 31.4 kg (−1.1 kg)
Girls · 1900
30.0 kg
Girls · 2015
43.6 kg
Girls · change over the record
+13.6 kg
Girls · highest
45.1 kg (1999)
Girls · 1939 to 1948
33.7 kg → 32.2 kg (−1.5 kg)
Boys
Girls
no survey
Table · Weight · Age 13 (lower secondary)
Table · Weight · Age 13 (lower secondary)
Measure
Value
Boys · 1900
33.0 kg
Boys · 2015
48.8 kg
Boys · change over the record
+15.8 kg
Boys · highest
50.6 kg (2001, 2002)
Boys · 1939 to 1948
36.9 kg → 34.5 kg (−2.4 kg)
Girls · 1900
33.0 kg
Girls · 2015
47.3 kg
Girls · change over the record
+14.3 kg
Girls · highest
48.3 kg (1998, 2000, 2001, 2002)
Girls · 1939 to 1948
38.2 kg → 35.9 kg (−2.3 kg)
Boys
Girls
no survey
Table · Weight · Age 14 (lower secondary)
Table · Weight · Age 14 (lower secondary)
Measure
Value
Boys · 1900
38.0 kg
Boys · 2015
53.9 kg
Boys · change over the record
+15.9 kg
Boys · highest
55.5 kg (2001, 2002)
Boys · 1939 to 1948
43.6 kg → 38.9 kg (−4.7 kg)
Girls · 1900
39.0 kg
Girls · 2015
49.9 kg
Girls · change over the record
+10.9 kg
Girls · highest
50.9 kg (2001, 2002, 2003)
Girls · 1939 to 1948
43.3 kg → 40.1 kg (−3.2 kg)
Boys
Girls
no survey
Table · Weight · Age 15 (upper secondary)
Table · Weight · Age 15 (upper secondary)
Measure
Value
Boys · 1900
43.0 kg
Boys · 2015
59.0 kg
Boys · change over the record
+16.0 kg
Boys · highest
60.4 kg (2003)
Boys · 1939 to 1948
48.6 kg → 44.0 kg (−4.6 kg)
Girls · 1900
42.0 kg
Girls · 2015
51.5 kg
Girls · change over the record
+9.5 kg
Girls · highest
52.5 kg (2004)
Girls · 1939 to 1948
45.0 kg → 43.9 kg (−1.1 kg)
Boys
Girls
no survey
Table · Weight · Age 16 (upper secondary)
Table · Weight · Age 16 (upper secondary)
Measure
Value
Boys · 1900
47.0 kg
Boys · 2015
60.6 kg
Boys · change over the record
+13.6 kg
Boys · highest
62.2 kg (2003, 2004, 2005)
Boys · 1939 to 1948
51.8 kg → 48.7 kg (−3.1 kg)
Girls · 1900
45.0 kg
Girls · 2015
52.6 kg
Girls · change over the record
+7.6 kg
Girls · highest
53.4 kg (2003, 2004, 2006)
Girls · 1939 to 1948
47.5 kg → 47.2 kg (−0.3 kg)
Boys
Girls
no survey
Table · Weight · Age 17 (upper secondary)
Table · Weight · Age 17 (upper secondary)
Measure
Value
Boys · 1900
50.0 kg
Boys · 2015
62.5 kg
Boys · change over the record
+12.5 kg
Boys · highest
63.9 kg (2006)
Boys · 1939 to 1948
53.9 kg → 51.7 kg (−2.2 kg)
Girls · 1900
47.0 kg
Girls · 2015
53.0 kg
Girls · change over the record
+6.0 kg
Girls · highest
53.7 kg (2005, 2006)
Girls · 1939 to 1948
48.8 kg → 49.1 kg (+0.3 kg)
Boys
Girls
no survey
Table · Leg length · Age 5 (kindergarten)
Table · Leg length · Age 5 (kindergarten)
Measure
Value
Boys · 1949
44.3 cm
Boys · 2015
48.6 cm
Boys · change over the record
+4.3 cm
Boys · highest
48.8 cm (1977, 2004, 2009, 2010)
Girls · 1949
44.0 cm
Girls · 2015
48.1 cm
Girls · change over the record
+4.1 cm
Girls · highest
48.4 cm (1977, 2004, 2005, 2009)
Boys
Girls
no survey
Table · Leg length · Age 6 (elementary)
Table · Leg length · Age 6 (elementary)
Measure
Value
Boys · 1937
46.4 cm
Boys · 2015
51.7 cm
Boys · change over the record
+5.3 cm
Boys · highest
51.8 cm (2001, 2004, 2007, 2009, 2010, 2013)
Girls · 1937
46.1 cm
Girls · 2015
51.1 cm
Girls · change over the record
+5.0 cm
Girls · highest
51.3 cm (1994, 1995, 2001, 2005, 2007, 2009, 2010)
Boys
Girls
no survey
Table · Leg length · Age 7 (elementary)
Table · Leg length · Age 7 (elementary)
Measure
Value
Boys · 1937
49.6 cm
Boys · 2015
54.9 cm
Boys · change over the record
+5.3 cm
Boys · highest
54.9 cm (2009, 2010, 2011, 2015)
Girls · 1937
48.7 cm
Girls · 2015
54.3 cm
Girls · change over the record
+5.6 cm
Girls · highest
54.4 cm (2002, 2005, 2006, 2008, 2009, 2010, 2011)
Boys
Girls
no survey
Table · Leg length · Age 8 (elementary)
Table · Leg length · Age 8 (elementary)
Measure
Value
Boys · 1937
52.3 cm
Boys · 2015
57.9 cm
Boys · change over the record
+5.6 cm
Boys · highest
58.0 cm (2006, 2009, 2011, 2013)
Girls · 1937
51.6 cm
Girls · 2015
57.4 cm
Girls · change over the record
+5.8 cm
Girls · highest
57.5 cm (1994, 1995, 2005, 2008, 2009, 2011, 2012, 2014)
Boys
Girls
no survey
Table · Leg length · Age 9 (elementary)
Table · Leg length · Age 9 (elementary)
Measure
Value
Boys · 1937
54.6 cm
Boys · 2015
60.9 cm
Boys · change over the record
+6.3 cm
Boys · highest
61.0 cm (2012, 2013, 2014)
Girls · 1937
54.3 cm
Girls · 2015
60.7 cm
Girls · change over the record
+6.4 cm
Girls · highest
60.8 cm (2008, 2009, 2010, 2011, 2012, 2013, 2014)
Boys
Girls
no survey
Table · Leg length · Age 10 (elementary)
Table · Leg length · Age 10 (elementary)
Measure
Value
Boys · 1937
57.4 cm
Boys · 2015
64.0 cm
Boys · change over the record
+6.6 cm
Boys · highest
64.0 cm (2012, 2013, 2014, 2015)
Girls · 1937
57.5 cm
Girls · 2015
64.3 cm
Girls · change over the record
+6.8 cm
Girls · highest
64.4 cm (2009)
Boys
Girls
no survey
Table · Leg length · Age 11 (elementary)
Table · Leg length · Age 11 (elementary)
Measure
Value
Boys · 1937
60.0 cm
Boys · 2015
67.5 cm
Boys · change over the record
+7.5 cm
Boys · highest
67.5 cm (2008, 2009, 2012, 2014, 2015)
Girls · 1937
59.5 cm
Girls · 2015
67.5 cm
Girls · change over the record
+8.0 cm
Girls · highest
67.6 cm (1999, 2000, 2001, 2003, 2005, 2006, 2009, 2010)
Boys
Girls
no survey
Table · Leg length · Age 12 (lower secondary)
Table · Leg length · Age 12 (lower secondary)
Measure
Value
Boys · 1937
62.7 cm
Boys · 2015
71.2 cm
Boys · change over the record
+8.5 cm
Boys · highest
71.4 cm (2000)
Girls · 1937
63.7 cm
Girls · 2015
69.7 cm
Girls · change over the record
+6.0 cm
Girls · highest
69.9 cm (1999, 2001, 2002, 2003, 2004, 2007, 2008)
Seventeen-year-old boys came out of the war 1.9 cm shorter than they went in, and it took until 1952 to get it back.
The last pre-war measurement was 1939: 162.5 cm. The survey then stopped for eight years. When it resumed in 1948 the figure was 160.6 cm — a fall of 1.9 cm, undoing more than fifteen years of gain.
Girls lost far less: 152.5 cm in 1939 against 152.1 cm in 1948, a fall of 0.4 cm. The asymmetry is in the record and the record does not explain it.
Recovery was not quick. Boys did not match their 1939 figure again until 1952, thirteen years later. Girls managed it by 1950.
One earlier year is missing too, 1921, for every age from six to seventeen.
04
Then the fastest growth in the record
From 1948 to 1990, seventeen-year-old boys gained 9.8 cm — more than twice what the previous half-century had delivered.
The four decades after the war added 9.8 cm to the average seventeen-year-old boy, against 4.6 cm across the thirty-nine years from 1900 to 1939. Nothing else in the record moves at that rate.
The survey widened as it went. Five-year-olds in kindergarten enter the record in 1948 and had not been counted before; their first two years of the 1950s, 1952 and 1953, are missing.
05
And then it stopped
Boys reached 170.9 cm in 1994 and have never exceeded it. Every year since sits within two millimetres of that figure.
170.9 cm was first recorded in 1994. It was matched in 1996, 1997, 1998, 1999, 2001 and 2006, and never beaten. By 2015 the figure was 170.7 cm. Girls did the same thing: 158.1 cm in 1994, matched four more times, 157.9 cm in 2015.
It would be wrong to call any of those years a peak. The survey samples schools rather than counting every child, so a tenth of a centimetre between two years is noise. What the record supports is not that Japanese children topped out on a particular date — it is that for the last two decades of measurement, they stopped getting taller at all.
Weight did the same. Seventeen-year-old boys averaged 62.0 kg in 1990 and 62.5 kg in 2015.
06
The part that kept changing
Since 1990 the average boy's legs have got 0.8 cm shorter while his seated height grew 1.1 cm. His total height did not move.
Japanese schools also measured sitting height — the height of a seated child, from the seat to the crown — from 1937 until the practice was abandoned after 2015. Subtracting it from standing height gives the length of the legs, and the legs are where the century's growth disproportionately went: from 1937 to 2015 total height rose 6.0% while leg length rose 7.4%.
But that trend reversed while nobody was looking. Between 1990 and 2015 the average seventeen-year-old boy's sitting height rose from 91.0 cm to 92.1 cm, and his legs shortened from 79.4 cm to 78.6 cm. Total height changed by 0.3 cm. A generation of Japanese teenagers is the same height as the one before it and differently proportioned.
Select leg length in the chart above to see it. The line ends in 2015 because the measurement does.