Walk into an urban high school and look around at the kids. Roughly half of them will drop out of school. If you knew which ones, you might be able to steer them toward a different path. But you can’t solve a problem until you can spot it, and how do you spot a future dropout?

Some Johns Hopkins University researchers, frustrated by the high-school-dropout rate, went looking for early-warning signs among students in Philadelphia. What were the telltale markers of a student who wouldn’t graduate? Their analysis came back with astonishing clarity. Poring over eighth-grade attendance records, they found hundreds of students who had missed more than one out of every five class days. Of those frequent absentees, 78% eventually quit high school. Similarly, of the eighth graders who had failed either English or math, three out of four dropped out. No other factor — gender, race, age, or standardized-test scores — had the predictive power of those two patterns.

The researchers concluded that the school district could identify more than half of the students who would be likely to drop out before they even set foot in high school.

The early-warning flags didn’t solve the dropout problem, of course, any more than a smoke alarm can put out a fire. But policy analysts at the National High School Center, armed with this information, were then able to review almost a dozen dropout-prevention programs with documented success that could be targeted toward the most at-risk kids.

What if you could identify the early-warning signs of a business problem? What if, in fact, the red flags are there right now, waving at you unheeded from information you’ve already collected?

Credit-card companies, for instance, have learned that by charting the “normal” spending habits of their cardholders, they can quickly spot fraudulent use. (Though sometimes the warnings of fraud can feel uncomfortably like character judgments, as when Dan bought flowers for his wife and AmEx, incredulous, immediately blocked his account.)

Google executives realized in November 2008 that flu outbreaks could be detected early by monitoring the number of times people searched for terms such as “flu” and “influenza.” Because the searches are logged instantly, epidemiologists can spot flu outbreaks a full one to two weeks faster than they could have before. Perhaps someday Google might reconfigure this technology to spot and quash boy bands before they can infect your daughters.