As more questions are added to the survey more women are required to complete the survey to insure that adequate numbers of women are in each cell. Survey results often report a margin of error. The error term means that if the survey was repeated with different samples of respondents, the results would be within the margin of the error. If a survey says that NFP use is 4 percent in the U.S. and the margin of error is 1 percent we expect another similar survey to say that NFP use in the U.S. is three, four, or five percent but not two or six or another percent. Reported differences outside the margin of error are what scientists call statistically significant differences.
Significant results require explanation to account for the differences.
The report is for currently married women, or women in union. Shown for comparison is the number of women using no method and the number using the pill. These data are representative of NFP use around the world. They are not interested in it, discourage its use, and provide no money for it. In my opinion, more couples would use it if they were given the choice.