The Sun Belt is a region of the United States generally considered stretching across the Southeast and Southwest. Another rough definition of the region is the area south of the 36th parallel. Several climates can be found in the region — desert/semi-desert (Eastern California, Nevada, Arizona, New Mexico, Utah, and West Texas), Mediterranean (California), humid subtropical (Alabama, Mississippi, Louisiana, Florida, Georgia, South Carolina, North Carolina, and Texas) and tropical (South Florida). 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. The Sun Belt comprises the southern tier of the United States, including the states of Alabama, Arizona, Florida, Georgia, Louisiana, Mississippi, New Mexico, South Carolina, Texas, roughly two-thirds of California (up to Greater Sacramento), and the southern parts of North Carolina, Nevada, and Utah. Five of the states—Arizona, California, Florida, Nevada, and Texas—are sometimes collectively called the Sand States because of their abundance of beaches or deserts.