Is the Billings Ovulation Method™ an "outdated" method?

The Billings Ovulation Method™ was first developed in the 1950s by Drs. John and Lynn Billings. 

The method was found to be highly effective (98.5% for postponing pregnancy) independently by the World Health Organization (WHO) in the 1970s. 

Research of the method has never ceased and continues today to be studied and refined world wide, with the focal point of research being done by the Ovulation Method Research and Reference Centre of Australia.

Other natural methods that were developed later, that used the Billings Ovulation Method™ as a base are not improvements on the Billings Ovulation Method™ rather they are just different methods.  They use different methodologies and may or may not be as well studied and/or effective.