When you enter phrases or key words into the Google Books Ngram Viewer, it displays a graph showing how many times those phrases have occurred in a corpus of books (here English-language books) over the selected years (here 1960 to 2008, last year of data availability). See Ngram 10 in “The perils of IVF, of ARTs, of giving birth at old age – part 2” at http://to.ly/d0iq . It shows the data for the number of books on IVF (blue) and for the number of books about the Pill (red). Books about the Pill appear and grow in numbers in the 1960s (when the Pill was launched in the market) while IVF books only appear some 10 years later. By 1980s the IVF book numbers grow fast and far exceed the number of books about the contraceptive Pill. Even more significantly, the IVF book volume does not exhibit a declining trend (such as occurs in the Pill data after 1980). IVF books continue to be written at a relatively steady rate, significantly higher in numbers than the declining books about the Pill.