Good job  I understood the points you wanted to convey  

Using the word "year" here is very formal. I just say "in 1984". 

the charts below compare the age distributions of France and India in 1984.

It is obvious that in India, there were more young people taking up the proportion of the total population. While in France, people in all age groups were distributed almost evenly with the number of the young people slightly surpassing the figure for the elderly people [unsure if you need the word people, Elderly. elderly].

the Indian population [or "India's population"] skews towards a younger demographic while the population in France is more evenly distributed across all age groups...

To be more specific, young Indians in 1984 aged from [remove aged or use "ranging in age from"] 0 to 30 took up nearly [represented] 70% of the India’s total population.

However In comparison, the same age group young people in France made [up] less than half of its total population. The same phenomenon that we can observe in both countries is that there was no significant difference in the number of males and females at the different ages groups/buckets.

What is the purpose of reiterating the year (1984)?

Furthermore, in 1984, France saw [experienced] a greater proportion of people lived [living] longer [as observed in the population above 70 years old (somehow you should end the sentence here and use the second sentence for a more brief comparison) with around 9 % of the French aged 70 and over. By contrast, it only shows a relatively smaller proportion, less than 3%, of Indians being over 70 years old. In fact, this paragraph belongs directly after the paragraph ending with "the elderly people"

you can use the word "comprised" when discussing percentages equaling 100%. Comprised is a good substitute for "made up". For example, the 70 and older age bracket comprised 3% of the total.