Since the early 1980s, the urban area of Beijing has expanded greatly with the completion of the 2nd Ring Road in 1981 and the subsequent addition of the 3rd, 4th, 5th and 6th Ring Roads. According to one 2005 newspaper report, the size of newly developed Beijing was one-and-a-half times larger than before. Wangfujing and Xidan have developed into flourishing shopping districts, while Zhongguancun has become a major center of electronics in China. In recent years, the expansion of Beijing has also brought to the forefront some problems of urbanization, such as heavy traffic, poor air quality, the loss of historic neighborhoods, and a significant influx of migrant workers from less-developed rural areas of the country.  Beijing has also been the location of many significant events in recent Chinese history, principally the Tiananmen Square protests of 1989. The city has also hosted major international events, including the 2008 Summer Olympics and the 2015 World Championships in Athletics, and was chosen to host the 2022 Winter Olympics, making it the first city to ever host both Winter and Summer Olympics.