Back in 2010, Tokyo, Japan had the biggest population of any city on the planet with a population of over 36 Million people. This was nearly 15 million more than Delhi, India, which had the second highest population.

Fast forward 90 years and Tokyo is predicted to not even make it into the top 20 cities in the world.

In fact, only six of the top 20 cities with the highest population in 2010 are predicted to still be in the top 20 by 2100.

In this research led piece, Roof Stores have been tracking the top 20 cities in the world with the highest population back in 2010 and following their projected population increase or decrease over the years.

The Top 10 Biggest Cities by Population in 2010 were:

1. Tokyo, Japan - 36,834,000
2. Delhi, India - 21,935,000
3. Mexico City, Mexico - 20,132,000
4. Shanghai, China - 19,980,000
5. São Paulo, Brazil - 19,660,000
6. Osaka, Japan - 19,492,000
7. Mumbai, India - 19,422,000
8. New York, United States of America - 18,365,000
9. Cairo, Egypt - 16,899,000
10. Beijing, China - 16,190,000

The Top 10 Biggest Cities by Population in 2025 are expected to be:

1. Tokyo, Japan - 36,400,000
2. Mumbai (Bombay), India - 26,385,000
3. Delhi, India - 22,498,000
4. Dhaka, Bangladesh - 22,015,000
5. Sao Paulo, Brazil - 21,428,000
6. Mexico City, Mexico - 21,009,000
7. New York City-Newark, USA - 20,628,000
8. Kolkata (Calcutta), India - 20,560,000
9. Shanghai, China - 19,412,000
10. Karachi, Pakistan - 19,095,000

The Top 10 Biggest Cities by Population in 2050 are expected to be:

1. Mumbai (Bombay), India - 42,403,631
2. Delhi, India - 36,156,789
3. Dhaka, Bangladesh - 35,193,184
4. Kinshasa, Democratic Republic of the Congo - 35,000,361
5. Kolkata (Calcutta), India - 33,042,208
6. Lagos, Nigeria - 32,629,709
7. Tokyo, Japan - 32,621,993
8. Karachi, Pakistan - 31,696,042
9. New York City-Newark, USA - 24,768,743
10. Mexico City, Mexico - 24,328,738

The Top 10 Biggest Cities by Population in 2075 are expected to be:

1. Kinshasa, Democratic Republic of Congo - 58,424,142
2. Mumbai, India - 57,862,345
3. Lagos, Nigeria - 57,195,075
4. Delhi, India - 49,338,148
5. Dhaka, Bangladesh - 46,218,971
6. Kolkata, India - 45,088,111
7. Karachi, Pakistan - 43,373,574
8. Dar Es Salaam, United Republic of Tanzania - 37,484,980
9. Cairo, Egypt - 32,999,203
10. Manila, Philippines - 32,748,758

The Top 10 Biggest Cities by Population in 2100 are expected to be:

1. Lagos, Nigeria - 88,344,661
2. Kinshasa, Democratic Republic of Congo - 83,493,793
3. Dar Es Salaam, United Republic of Tanzania - 73,678,022
4. Mumbai, India - 67,239,804
5. Delhi, India - 57,334,134
6. Khartoum, Sudan - 56,594,472
7. Niamey, Niger - 56,149,130
8. Dhaka, Bangladesh - 54,249,845
9. Kolkata, India - 52,395,315
10. Kabul, Afghanistan - 50,269,659