Probabilities of failing birth control methods

In high school health class, where I learned about contraceptives and the dangers of pre-marital sex, my teacher spouted rates to scare. He would say something like condoms are 98 percent effective but never explained what that meant. Do they break 2 percent of the time? Do couples get pregnant 2 percent of the time? STDs?

These charts from Gregor Aisch and Bill Marsh might help. They show the probability of an unplanned pregnancy, categorized by contraceptive and over a span of ten years. The top solid lines represent probabilities with “typical use” and the dashed lines on the bottom represent probabilities with “perfect use.”

Maybe it’s time for better instructions on how to use these things.

Update: The calculation of long-term probabilities is likely on the pessimistic side and makes too many assumptions about the data and population. Andrew Whitby critiques.

Favorites

The Best Data Visualization Projects of 2014

It’s always tough to pick my favorite visualization projects. Nevertheless, I gave it a go.

Where Bars Outnumber Grocery Stores

A closer look at the age old question of where there are more bars than grocery stores, and vice versa.

Marrying Age

People get married at various ages, but there are definite trends that vary across demographic groups. What do these trends look like?

Watching the growth of Walmart – now with 100% more Sam’s Club

The ever so popular Walmart growth map gets an update, and yes, it still looks like a wildfire. Sam’s Club follows soon after, although not nearly as vigorously.