Certain types of birth control, like Depo-Provera and birth control pills ("the Pill"), are more than 99-percent effective. But that's only if they're used properly. Human error ("oops, I forgot my pill") is a huge factor in whether birth control works.

It's so important that manufacturers actually have two different rates of effectiveness for birth control. One is with "perfect use" in a laboratory, where there's no room for mistakes. The other is the "typical" rate, which takes into account the occasional broken condom and the couple of nights you forgot your pill. Of course, the perfect use rate is always higher.

Here are the effective rates in percentages (both "perfect use" and "typical use"):

Abstinence
Prefect Use: 100%
Typical Use: 75%

Birth Control Pill ("the Pill")
Perfect Use: 99.7%
Typical Use: 92%

Condoms
Male
Perfect Use: 98%
Typical Use: 85%
Female
Perfect Use:95%
Typical Use: 79%

Withdrawal ("pulling out")
Perfect Use: 96%
Typical Use: 73%

Depo-Provera ("the shot")
Perfect Use: 99.7%
Typical Use: 97%

NuvaRing
Perfect Use: 99.7%
Typical Use: 92%

Ortho Evra ("the Patch")
Perfect Use: 99.7%
Typical Use: 92%

Seasonale
Perfect Use: 99.7%
Typical Use:  92%

Spermicides--alone
Perfect Use: 82%
Typical Use: 71%

Cervical Cap
Perfect Use: 91%
Typical Use: 84%

Diaphragm
Perfect Use: 94%
Typical Use: 84%

Intrauterine Device (IUD)
Perfect Use: 99%
Typical Use: 98-99%

By the way, 85 percent of couples who do not use ANY method of birth control will become pregnant in a year.

For more information and photos of birth control methods, check out the story "An A to Z of Contraception" by Staff Writer Claire Marchetta.