Final answer:
The withdrawal method is less effective because preejaculatory fluid from the bulbourethral gland can contain sperm that may lead to pregnancy, resulting in a typical use failure rate of approximately 22 percent.
Step-by-step explanation:
Withdrawal has relatively low effectiveness as a contraceptive method due to the presence of preejaculatory fluid. The bulbourethral gland, or Cowper's gland, releases this fluid before ejaculation, neutralizing any acid residue in the urethra from urine. Even before the man withdraws, the preejaculatory fluid can contain sperm that might fertilize an egg, leading to potential pregnancy. Therefore, withdrawal has a higher failure rate than some other contraceptive methods, with typical use failure rate estimated around 22 percent.