Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
interpolate((1915,4.156),(1922, 4.857),(1946, 7.16),(1991, 29.989))
interpolate((1915,4.156),(1922, 4.857),(1946, 7.16),(1991, 29.989))
Natural Language
Math Input
Extended Keyboard
