Independent variable

Value

Age

Numerical variable ranging from 20 to 82

Gender

1 if male; 0 if female

Employment

1 if full-time; 0 otherwise

Income

Categorical variable representing income, in million yen per year (categories: 2<, 2 - 3.99, 4 - 5.99, 6 - 7.99, 8 - 9.99, 10 - 11.99, 12 - 14.99, 15 - 19.99, 20≤)

Altruistic orientation

Numerical variable ranging from 10 to 50