In the year of 1940, the percentage of elderly people stood at 5% in japan, about 7% in Sweden and around 9% in the United States. And the ratio of senior citizens in Japan dropped to 3% and remained steady to 2000. However, Sweden had an opposite trend , the percentage continuously increased from 1960 to 2040 with a slight dip in 1990 and 2020. In the states, the percentage stayed almost steady at about 15% from the year of 1980 to 2020.