Paragraph 1: yes they have been left behind. What are the negative aspects to economic development/ urban expansion? What are the conditions like between urban and rural areas, why are these differences so bad? What are some of the negative consequences to people moving to the cities for work?
Paragraph 2: no they havent been left behind. What are the positives of people moving to the cities for work? What are the positives of economic growth- do any of these out weigh the negatives?
Conclusion: What do you think- dont just repeat your points say which you agree with, pick the most significant factor to support your point. Take a step back and see the bigger picture