Excel calculates values following logistic growth and can chart them on a line graph. Type "=A1/(1+B1exp(C1D1))" without quotes into an Excel cell. Type the value of the function's "N" constant ...

Logistic fits using data up to 1989, 1999 or 2009 forecast an ultimate coal reserve of 52, 71 or 96 gigatonnes, respectively, and predict that production should have peaked in 1951, 1967 or 1986.