Dr. Gamble and his workers explained and promoted simple methods—not the expensive and often impractical diaphragm, but spermicidal jellies, foam powders, sponges to be dipped in salt or other inexpensive solutions—to women who otherwise would never have known of nor been able to afford contraceptives. At the same time, he recognized the need for scientific data to back his promotion of the simple methods, and he set up extensive clinical trials, with his visiting nurses collecting data that measured the effectiveness of the simple methods. Again and again, it was shown that birth rates were reduced by as much as two-thirds or more using these simple methods.