"According to the first line graph, the world population has increased substantially from about 3 billion in 1950 to around 7 billion, and this..."

[hardyweineberg]

This paragraph is from my essay, and I have only 1 question.

"According to the first line graph, the world population has increased substantially from about 3 billion in 1950 to around 7 billion, and this significant growth is expected to continue until 2100, when it is expected to be roughly 11 billion. Rising from just below 2 billion in 1950 to slightly above 6 billion in 2100, the 15-64 year old population has and will be mainly responsible for this huge growth in the world population."

"Additionally, the number of people below 5 years and the number below 15 years remain relatively stable, at around 1 billion and at just under 2 billion respectively." (NOTE: I wrote remain instead of have remained and will remain)


If I have to describe information that was, is, and will still be true, can I simply used a present tense verb such as "is" rather than writing "has and will be"?

So rather than saying "...the 15-64 year old population has and will be mainly responsible for this huge growth...", I'd say "...the 15-64 year old population is mainly responsible for this huge growth..."

 

[5jj]

the 15-64 year old population has and will be mainly responsible for this huge growth in the world population."

This should be ... has been and will (continue to) be ... . Your is does not convey the same message.