If you look at PWC list rankings, Not only are Mumbai, Delhi and Kolkata FAR ahead of Dhaka by economic size. Cities like Bangalore, Chennai, and Hyderabad are not too far behind. Their economic sizes are 88%, 85% and 75% of Dhaka Economic size (and mind you their total populations are much less than Dhaka).
These percentages only increase in the 2025 projection by PWC (suggesting faster economic growth in Indian cities predicted)...and even cities like Ahmedabad by 2025 is going to be 67% of Dhaka economic size....and Surat about 50%.
Your Chittagong is ranked below Jaipur, Kanpur and is just a touch above Lucknow....and you are saying Kolkata is like Chittagong.
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And now you are saying only Maharahstra is the only state comparable to Bangladesh GDP?
In 2014, Bangladesh had a total GDP of about 1.1 million crore INR. Maharashtra was about 1.4 times this amount (with a population only about 70% of Bangladesh).
Tamil Nadu was about 90% the GDP of Bangladesh GDP (population less than half of Bangladesh)
Uttar Pradesh was about 90% of Bangladesh GDP (population 1.3 times that of Bangladesh)
West Bengal was about 64% of GDP of Bangladesh (population about 60% of Bangladesh)
Gujarat was about 70% of GDP of Bangladesh (population about 40% of Bangladesh)
Even States like Rajasthan, Madhya Pradesh, Karnataka are significant portions of Bangladesh GDP (about 50% range)...and their populations are never more than 50% of Bangladesh (Karnataka is only 40%).
So dont ever go spouting off that Maharashtra is the only state who's GDP is "comparable" to Bangladesh.
You can check all these figures yourself:
List of Indian states by GDP - Wikipedia, the free encyclopedia
List of countries by GDP (nominal) - Wikipedia, the free encyclopedia
Reference: 185 billion USD GDP of Bangladesh in 2014 ~ 1.1 million crore INR in 2014.