It is true that more and more people are residing in mega-cities with populations exceeding 20 million. From my perspective, this tendency brings more disadvantages than advantages.
It is undeniable that metropolises bring considerable economic opportunities. Firstly, job markets in these areas are more diverse and the salaries are much higher than rural areas. Due to the variety of employments in mega-cities, citizens are able to apply for one to two jobs to make a good living; besides, the salaries in big cities are also higher which provide human with a better standard of living than in the rural areas. Secondly, metropolises attract many prestigious universities along with leading research institutions. This helps residents easily access to high-quality education and permanent learning opportunities that enhancing their professional qualifications and allowing individuals to work abroad.
However, I strongly believe the drawbacks caused by mega-cities are far more serious. One disadvantage is that population overload lead to housing shortages and limited public spaces. As a result, many residents have to live in slums or become homeless to make ends meet in big cities; moreover, limited public spaces also leads to traffic congestion and lengthy commutes which badly affect citizens. In addition, pollution is also an intractable problem in many metropolises. Due to the high numbers of industrial activities and an overload of private vehicles, air quality is seriously deteriorate in many mega-cities such as Beijing and Delhi, which leads to the increase of respiratory diseases and other health problems.
In conclusion, it can be easily seen that mega-cities bring economic and education advantages for citizens. However, along with the advantages, metropolises also have many negative impacts on the environment and quality of life.