By the 1990s, crime rates started to drop dramatically due to revised police strategies, improving economic opportunities, gentrification, and new residents, both American transplants and new immigrants from Asia and Latin America. Murder rates that had reached 2,245 in 1990 plummeted to 537 by 2008, and the crack epidemic and its associated drug-related violence came under greater control. The outflow of population turned around, as the city once again became the destination of immigrants from around the world, joining with low interest rates and Wall Street bonuses to fuel the growth of the real estate market. Important new sectors, such as Silicon Alley, emerged in Manhattan's economy. 21st century On September 11, 2001, two of four hijacked planes were flown into the Twin Towers of the original World Trade Center, and the towers subsequently collapsed. 7 World Trade Center collapsed due to fires and structural damage caused by heavy debris falling from the collapse of the Twin Towers. The other buildings within the World Trade Center complex were damaged beyond repair and soon after demolished. The collapse of the Twin Towers caused extensive damage to other surrounding buildings and skyscrapers in Lower Manhattan, and resulted in the deaths of 2,606 people, in addition to those on the planes. Many rescue workers and residents of the area developed several life-threatening illnesses that have led to some of their subsequent deaths. Since 2001, most of Lower Manhattan has been restored, although there has been controversy surrounding the rebuilding. A memorial at the site was opened to the public on September 11, 2011, and the museum opened in 2014. In 2014, the new One World Trade Center, at and formerly known as the Freedom Tower, became the tallest building in the Western Hemisphere, while other skyscrapers were under construction at the site. The Occupy Wall Street protests in Zuccotti Park in the Financial District of Lower Manhattan began on September 17, 2011, receiving global attention and spawning the Occupy movement against social and economic inequality worldwide. On October 29 and 30, 2012, Hurricane Sandy caused extensive destruction in the borough, ravaging portions of Lower Manhattan with record-high storm surge from New York Harbor, severe flooding, and high winds, causing power outages for hundreds of thousands of city residents and leading to gasoline shortages and disruption of mass transit systems. The storm and its profound impacts have prompted the discussion of constructing seawalls and