What thirty percent actually means

A headline says a food raises cancer risk by thirty percent. Sounds like a coin flip. It almost never is, because headlines quote relative risk and hide the number that matters: the baseline.

If a cancer affects 4 people in 100 over a lifetime, a thirty percent increase moves that to roughly 5 in 100. One additional case per hundred people, across entire lifetimes of exposure. Real, worth knowing, and nothing like the panic the headline sells.

The question to ask of every risk number is: thirty percent of what? If the article does not tell you the baseline, it is not informing you, it is farming your attention.

The same arithmetic works in your favour with screenings. A screening that cuts mortality by twenty percent sounds modest, but applied to a common disease across a whole population, it is thousands of lives. Baselines cut both ways.

Prevention and Screening keeps a plain risk reader for exactly this: paste the claim, see the baseline arithmetic, decide with a level head. Numbers should inform you. They should never own you.