instruction: What are the causes of population growth in the Sun Belt in the US?
context: The Sun Belt has seen substantial population growth since post-World War II from an influx of people seeking a warm and sunny climate, a surge in retiring baby boomers, and growing economic opportunities. The advent of air conditioning created more comfortable summer conditions and allowed more manufacturing and industry to locate in the Sun Belt. Since much of the construction in the Sun Belt is new or recent, housing styles and design are often modern and open. Recreational opportunities in the Sun Belt are often not tied strictly to one season, and many tourist and resort cities, such as Fort Lauderdale, Gulf Shores, Houston, Las Vegas, Los Angeles, Miami, Myrtle Beach, New Orleans, Orlando, Palm Springs, Phoenix, San Antonio, San Diego, Tampa, and Tucson support a tourist industry all year.
  The traditional explanations for the growth are increasing productivity in the South and West and increasing demand for Sunbelt amenities, especially its pleasant weather. Job decline in the Rust Belt is another major reason for migration.
response: Since WWII, many people have migrated from the US Midwest or Northeast to the Sun Belt. One significant factor is the milder climate and the recreational possibilities it makes possible. Economic opportunity is another factor, as many automobile and other manufacturers have left the Midwest and Northeast and built factories in the Sun Belt. The housing stock is newer and affordable, which attracts people of all ages.