"Cuts your risk 50%" vs. what actually changes

"New drug cuts your risk of a heart attack in half" sounds enormous. But cut in half from what? If your risk drops from 2 in 100 to 1 in 100, that is technically a 50% reduction, and it is also a change of just one person in a hundred. Both numbers are true. One is designed to impress you, and one tells you what actually changed.

The impressive-sounding one is the relative risk. It compares the two groups as a ratio, so a drop from 2% to 1% becomes "50% lower." The plain one is the absolute risk, the actual difference in your chances, which here is one percentage point. Headlines and press releases almost always reach for the relative number, because bigger sounds better.

Neither number is a lie, but the relative number without the absolute number is missing the part you need. A 50% reduction of a large risk is a genuinely big deal. A 50% reduction of a tiny risk is often barely worth noticing. You cannot tell which one you are looking at unless you know the starting risk.

So whenever you see a percentage reduction, ask two questions the headline usually skips: from what, and to what, in real numbers? "From 2 in 100 to 1 in 100" tells you far more than "cuts risk 50%." Once you start asking for the absolute numbers, a lot of scary and a lot of miraculous headlines shrink back to their true size.