The Heritage Action Artefact Erosion Counter indicates that half a million artefacts have been dug up in just 21 months (Heritage Action: 'British artefact hunting: “the envy of the world”!' 21/05/2016):
We’ve always said 70% of them don’t get reported but the Portable Antiquities Scheme disagrees, saying only 66% aren’t reported. We’ll settle for that. Here’s what it means: if each unrecorded find is an inch wide then our country is allowing 4.5 miles of artefacts to disappear unreported every year. Or if you prefer, in the 18 years since this spiffing system began, they’d stretch from the PAS office in Bloomsbury to English Heritage’s office in Swindon.That's pretty shocking in itself, what is more shocking is that so few people (ie heritage action and myself in effect) are actively discussing it.