Jobs, jobs, jobs. The day after Labor Day millions of Americans are wondering when their next chance for employment will come. The nation's unemployment rate stands at 9.1 percent and experts believe it's going to take years before it goes back down to normal. Ryan Avent, economics correspondent at The Economist, believes the number of jobs available could rise if a city's population density rises. He wrote in The New York Times about what other ingredients need to be mixed in with a dense population to create a healthy economy.