Your first sentence for writing task 1 should be a paraphrase of the question.
Paraphrasing, we might write:
The line graph illustrates the percentage of people who are at least 65 years old in Japan, Sweden and USA from 1940 to 2040.
Here are a few commonly used synonyms and alternative phrases to help you paraphrase Task 1 questions:
• line graph = graph
• bar chart = chart / graph
• shows = gives information about = illustrates = (The pie chart) gives a breakdown of = (The map) is of
Do not copy the word ‘below’ from the question because there will be no graph below your answer!
• percentage of = proportion of = ratio of
• number of = figures for
• the population = people
• (aged) xx and over = (who are) at least xx
• between 19xx and 19yy = from 19xx to 19yy = over a zz-year period
• in three different countries = in [country 1], [country 2] and [country 3]