The below line graph depicts the distribution of population aged not less than 65 from 1940 to 2040 in three developed countries,including Japan,Sweden and USA.
It is clear that the most significant change of the proportion of old people happens in Japan,from the lowest to the highest with a fluctuated trend,while the trend of USA and Sweden are relatively more similar.
In the beginning,only 5% of population were aged 65 and beyond in Japan in 1940s.Over the past 40 years,from 1940 to 1980,the number even decreaseed,which reached the lowest point around 3%.After that,it began increasing slowly to 10% in the end of 2030.Notably,the rest 10 years,from 2030 to 2040,the proportion are swiftly raising,reaching the peak over 25% in 2040.
Compared to Japan,the other two countries,USA and Sweden,have similar trends,which began with a slight increase(USA 9%,Sweden 7%),than decreased a little and eventually had a more apparent raising,while the proportion of USA was higher at first but lower in the end.The important point happen in about 1990,when the both counries had gone through a small reduce of proportion by 2% from around 15%.The number of Sweden seriously fluctuated seriously,which reached even at the peak of 20%.In the end,the proportion of these countries stop at 25%(Sweden) and 23.5%(USA).