IELTS Writing task 1

Please help me.

The bar chart manifests the proportion of the total world population in India, China, the USA, Japan from 1950 to 2002 and projections for 2050.
Overall, it is clear that the percentage of the population of China is the highest of the 4 countries but it is the best reduced. China was followed by India, the USA was shorter than India and Japan were the shortest. From 1950 to 2050, 4 countries fluctuated, but China, the USA, and Japan decreased while India increased.
Especially, in 1950 proportion of China's population was the highest, it peaked at about 23%. Then China plummeted rapidly in 2002 with 20% and it was guessed that it will go down significantly in 2050 only 15%. Also, the USA declined from around 7% was one-third of China in 1950 to 5% in 2002 and it will stable in 2050. Japan is the shortest, in 1950 the percentage of Japan was approximately 4% and it fell gradually in the next 100 years.
In contrast, while China, the USA, Japan went down, India grow significantly from 15% in 1950 to about 17% in 2002 and it will surge around 19% in 2050.