Students learn in microeconomics that the demand curve for a good, which shows the relationship between the price of a good and the quantity of the good that consumers demand-i.e. are willing, ready, and able to purchase-has a negative slope.
The UNICEF estimates that an average of 353,000 babies are born each day around the world. The crude birth rate is 18.9 births per 1,000 population or 255 births globally per minute or 4.3 births every second (as of Dec. 2013 estimate).
Twin Births in the U.S., Like Never Before. More twins are being born in the United States than ever before. From 1980 to 2009, according to a recent report by the National Center for Health Statistics, the rate of twin births rose 76 percent. Now about one in 30 babies born in the United States is a twin.