Who provides the stats?
The Guttmacher Institute in 1968 was founded as the Center for Family Planning Program Development, a semi-autonomous division of the Planned Parenthood Federation of America. The Center was renamed in memory of Alan Frank Guttmacher, an Ob/Gyn and former president of Planned Parenthood, and the Guttmacher Institute became an independent, not-for-profit corporation in 1977.
CDC as well, I take it that the author is making deductions here based on the data.