Stock markets around the world are tumbling because of bad news from China. The Shanghai Index fell 8.5 percent, and Japan's Nikkei lost more than 4 percent. Top European markets opened lower as well. The Dow Jones Industrials are already coming off their worst week in four years, losing more than 1,000 points. CBS News financial contributor Mellody Hobson joins “CBS This Morning” from Chicago to discuss the market fallout.