Table 2 Definition of the variables

Academic performance (ACADEMIC)

Self-assessment of “Average of all Subjects” at age 15 on a five-point Likert scale, with 1 being the lowest and 5 being the highest performance.

Height (HEIGHT)

Height in meters at the time of the survey.

Education (EDUCATION)

Highest level of education completed. For Japan, from 1 = “Grade School” to 11 = “Doctoral Degree.” For the U.S., from 1 = “Grade School” to 9 = “Doctoral Degree.” For India, from 1 = “Illiterate” to 8 = “Graduate/ Post-Graduate-Professional.”

Marital status (MARRIAGE)

1 = married, 0 = otherwise

BMI (BMI)

Weight in kilograms divided by the square of height in meters (kg/m²).

Personal Income (INCOME)

Annual personal income (before taxes and including bonuses). JPY 1 million for Japan, USD 10 thousand for the U.S. and INR 10 thousand for India. Housewives/househusbands, students, and retired individuals are excluded. For Japan and the U.S., respondents chose from 1 = “No income” to 10 = to “14 million JPY (140 thousand USD) or more.” The lognormal distribution was applied to the frequency distribution to estimate the class values. For India, monthly income (10 thousand rupees) multiplied by 12.

Health (HEALTH)

Self-assessment of health status at the time of response on a five-point Likert scale: from 1 = “not good” to 5 = “good.”

Happiness (HAPPINESS)

Self-assessment of happiness at the time of response, from 0 = “very unhappy” to 10 = “very happy.”

Low birthweight (LBW)

1 = weighing less than 2.5 kg, 0 = otherwise

High birthweight (HBW)

For Japan, 1 = weighing more than 4 kg, 0 = otherwise. For the U.S., 1 = weighing 4–4.499 kg, 0 = otherwise.

Quasi-high birthweight (Q_HBW)

For India, 1 = weighing more than 3.5 kg, 0 = otherwise.

Very high birthweight (V_HBW)

For the U.S., 1 = weighing more than 4.5 kg, 0 = otherwise.

Do not know (DONTKNOW)

1 = do not know the birthweight, 0 = otherwise

Age (AGE)

Respondent’s age

Age-squared (AGESQ)

Squared term of the respondent’s age

Old age dummy (OLD)

1 = the respondent’s age is higher than or equal to 50 years old, 0 = otherwise.

Gender (MALE)

1 = male, 0 = female

Father’s education (F_EDUCATION)

Education level of the respondent’s father

Mother’s education (M_EDUCATION)

Education level of the respondent’s mother

Father’s age at birth (F_AGE_BIRTH)

Father’s age when the respondent was born.

Mother’s age at birth (M_AGE_BIRTH)

Mother’s age when the respondent was born.

Mothers’ employment status dummy

Mother’s employment status when the respondent was 15 years old. Full-time worker (M_FULLTIME), part-time worker (M_PARTTIME), housewife (M_HOUSEWIFE)

Standard of living at age 15 (S_LIVING)

Self-assessment of “Standard of living” at the age of 15 years, on a 11-point Likert scale, from 0 = “lowest” to 10 = “highest.”

Only child dummy (ONLYCHILD)

1 = no siblings at age 15, 0 = otherwise

Religious beliefs (RELIGION)

Self-assessment of degree of religious beliefs at the time of response, with 1 = “doesn’t hold true at all” to 5 = “particularly true” to the statement “I am deeply religious.”