descript the graph which shows the rate of old population in three different countries

The given graph illustrates the rate of aged people in one hundred years up to 2040 in three nations, namely the USA, Sweden and Japan. Initially, the USA had the highest figure among the three, standing at 9% and reaching a peak at 15% in the early 1980s, following by a relatively stable duration until 2020. The data for Sweden was 2% lower than that for the USA in 1940 but rose more significantly which almost tripled in 2010, though slightly declined after that, but still 4% higher than that for the USA, positioning at 19% in 2020. Opposite to the two other countries, starting at 5%, the proportion of elders in Japan marginally dipped to 4% in 1960 and kept this until 2000 when it nearly grew back to the initial value. Even though in the next two decades, Japan witnessed a climb in the elderly percentage, it was just at the same level as that of Sweden from the beginning of the period. However, in the rest of the period, it is predicted that the portion of Japanese old people will rocket to 27%, 2% and 4% higher than Sweden and the USA relatively. To sum up, in a century from 1940, the aged population rates of the USA and Sweden have a volatile upward trend, whereas that of Japan remained lower and stable in the first 80 year then will suddenly surge to first place eventually.