The number of census workers hired to count China's population will be bigger than the entire population of many nations. Some 6 million workers will fan out across China to count some 1.3 billion people—in a total of just 10 days. It's China's first census in 10 years, and authorities hope the biggest tally in the world will help determine how many children live in China. With the one-child-a-couple rule, many parents never register their "extra" kids. Officials also hope to pinpoint the number of migrant workers, which they believe is some 200 million, reports the BBC. (More China stories.)