The graph illustrates changes in the proportion of the population aged 65 and over form 1940 to 2040 in Japan,Sweden,and USA.（介词in用的没错,但要加上逗号.）
In 1940,JAPAN was the least in amount of population aged over 65,which was 5%.While the American population was the most proportion,which was double of Japanese about 9%,furthermore,Swiss population was 7% in between.
---In 1940,Japan was the one which has the least amount of population aged 65 and over(5%),while America consists of the largest proportion,which amounts to 9%,doubling that of Japan.
During 100-year period,proportion of Swiss and American had a upward trend,which increased to 25% and 27% respectively.but there was a slight decline in the number of Swiss population from 2010 to 2030.
However,the proportion of Japanese population witnessed a downward trend from 1940 to 1990,which reached the bottom (about 3%),after which,we can see a highly upward trend that the population increased to 27% in 2040.Furthermore,it even overtook Swiss and America in 2030.
Overall,the graph shows the proportion of three country’s population aged 65 and over has increased dramatically in 100 years.