When a child loses a baby tooth, an old U.S. tradition is for the tooth to be put under the child’s pillow, so that the tooth fairy will leave money for it. A survey by a Northwestern University professor [19] estimated that the tooth fairy paid an average of 12 cents for a tooth in 1900 and 1 dollar for a tooth in 1987. Using a base of 100 in 1967, the CPI was 25 in 1900, 340.4 in 1987, and 653.2 in 2010. Did the real value of tooth fairy payments rise or fall between 1900 and 1987? If tooth fairy payments had kept up with inflation between 1900 and 2010, how large should the 2010 payment have been?