No one was promising to halve the number of benefit-dependent teen mums but that is what happened. And it has taken just five years.
In 2010 there were 4502 teenagers with a child included in their main benefit. Today there are 2057.
The drop is astonishing.
Abortions are down, too.
They peaked for 15-19 year olds at 4173 in 2007 and dropped to 1635 last year. That's a 60 per cent drop.
Similar drops have been reported in England, Wales and the US.
Surveys in the US show teens having less sex. No one knows why.
Teenage mums typically stay benefit-dependent for 20 years. Thirty per cent stay trapped their entire working lives.
It's an almost surefire way to be poor and, sadly, their children appear disproportionately in all bad statistics.
The huge drop in benefit-dependent teenage mums bodes well for the future.
We seldom see a turnaround in negative social statistics and never one as dramatic or as significant as this.
It would be nice to attribute it to some new, enlightened policy, or better education, but there's nothing apparent to pin it to. The cause is a mystery.
One suggestion gaining currency is the ready availability of broadband and the rise of social media.
Teenagers spend more and more time on Facebook, Instagram and Twitter and the theory follows that teens socialise online rather than down at the park with a bottle of vodka. Certainly the timing fits. But I suspect the suggestion is altogether too prissy. Facebook and Twitter are fun but not that much fun.
I suggest the more likely reason is teenagers doing their sexual exploration online by sending each other naughty pictures and watching porn. They're the online generation, and find that easier, more comfortable and safer than the old-fashioned fumbling in the back of a car.
If that's the case, the internet sex that's bothering us all has a big upside. The fibre rollout is the best social policy any government has undertaken anywhere at any time.