Treasure Trace: Why does it go Wibble-wobble-blip?

I am still concerned about that UK Treasure Trace, the oft-published graph of the increase in Treasure reported from England and Wales and what it means (here and here). British archaeological Treasure-find jubilation has for long gaily treated the archaeological resource that this Treasure is coming from as, in effect, inexhaustible.   But of course it is not. Once all the Roman-period metalwork hoards in Britain have been dug up, then there will be no more (save invading a foreign country annexing its territory and looting more there too).

As I pointed out earlier, in the period 1997-2007 the graph goes up more or less in line with the estimated rise in numbers of active metal detectorists in England and Wales. The more detectorists there are, the more Treasure is found. There comes a point however where the increase in hoards being found does not correlate with the estimated numbers of detectorists active in the area at the time. It looks as if this started happening 2007-ish. When the PAS had been active just over a decade. Then the number of Treasure finds starts dropping off relative to the number of people thought to be active in the hobby.

It seems to me that, unless somebody can come up with a better explanation, this is because we had by this time reached a point where there are so few Treasure finds left in the accessible parts of the British archaeological record, that it was becoming harder to find a hoard than it was in the earlier days of 'metal detecting' in England and Wales.

I think the graph can show this in another way. While in the period 1996/7 (the new Treasure Act) to 2011 (with a minor wobble earlier), each year could be excitedly announced by archaeologist and collector alike as "more Treasure than last year!" (and examples of such jubilation can easily be found in the media), the situation changes after that.

After 2011, we start to hear the "more than/almost a thousand Treasure finds a year" mantra. This is because about 2011, the curve levels out. There is from this point forward no consistent rise as there had been before. Indeed some years it drops below the previous year's "haul". This to me suggests that the finding of Treasure has by this time become a much more random process than it had been up to about 2011. I am convinced this is because the resources of Treasure are now at critical level, and finding them is now harder.

I think the 2017 blip may be due to a whole lot of new people taking up the hobby about this time (and suggest, though place no emphasis on the idea, that this might be due to a popular British TV series encouraging Collection-Driven Exploitation of the archaeological record). A temporary surge of numbers of people will lead to a greater rate of Treasure finds relative to the background. 

We wait to see the 2019 results to see where the trend is going.

I used to ask, "when will this disregard of the damage done by the hobby end, when the archaeological resource is completely used up?" It seems to me that these figures suggest that we are indeed approaching a situation when that is the case. And that gives me no satisfaction at all.