Instructions: The task is about reading the given story and question, then finding an answer to the given question. Based on the passage provided and the given question, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
Input: story: Karachi (; ALA-LC: , ; ) is the capital of the Pakistani province of Sindh. It is the most populous city in Pakistan, sixth most populous city proper in the world and the 8th most populous metropolitan city in the world. Ranked as a beta world city, the city is Pakistan's premier industrial and financial centre. Karachi is also Pakistan's most cosmopolitan city. Situated on the Arabian Sea, Karachi serves as a transport hub, and is home to two of Pakistan's two largest seaports, the Port of Karachi and Port Bin Qasim, as well as the busiest airport in Pakistan.

Though the Karachi region has been inhabited for millennia, the city was founded as a fortified village named "Kolachi" in 1729. The settlement drastically increased in importance with the arrival of British East India company in the mid 19th century, who not only embarked on major works to transform the city into a major seaport, but also connected it with their extensive railway network. By the time of the Partition of British India, the city was the largest in Sindh with an estimated population of 400,000. Following the independence of Pakistan, the city's population increased dramatically with the arrival of hundreds of thousands of Muslim refugees from India. The city experienced rapid economic growth following independence, attracting migrants from throughout Pakistan and South Asia., question: When did the population increase?
Output:
Following the independence of Pakistan