The way I have always looked at it, if I am there at the moment, two others have been there before me, and four others before them, ad infinitum. So basically, almost everywhere has had some sort of activity in the past, and is worth a shot.
To put that to the test, consider the following:
Row crop land where I'm at (lettuce, broccoli, sugar beets, etc...) has gone on since about the 1920s'. Prior to that, our area was mostly cattle land. Thus since *at least* the 1920s, there's been continuous cultivation on various parcels of land. Field workers harvesting, thinning, picking, weeding, etc.... at various intervals for nearly 100 yrs. now. Thus logically, eventually, some coins should be introduced, right ? Sure not as concentrated as 3000 yrs. of some European continually cultivated fields, but ..... using your logic, "still worth a shot", right ?
But consider the following: There's a certain cultivated field in my area, that we hunt because it butts up near to a historic site. It had a small community living there @ the 1790s to 1820's. After that, it sat naked (cattle grazing at best), till the current era of agriculture, which began in these zones @ the 1920s (approaching 100 yrs. now).
So naturally, when my buddies and I hunt here, we are *OF COURSE* looking for reales and buttons of the earlier era. We could CARE LESS about a random buffalo nickel, or wheatie or whatever. Yet as you say: Yes, an occasional nuisance silver washington, or buffalo, or wheatie does surface.
And since we are in relic mindset, we're digging all conductive targets, for the last 15+ yrs. at this spot, during each fallow seasonal time. And this has given me a good statistical look at the productivity of the "random losses" logic, since I have kept accurate tallies of all targets found. And with that in mind, I have to say, that if someone were hunting these type fields, for the "random passerby/fieldworker losses", it simply wouldn't be worth it. Sure, after 10 hunts, one of us finds a wheatie or silver roosie. But seriously, given the hours spent, and the aluminum shrapnel that is encountered, we could certainly find more productive areas, if that was our objective.
I suppose areas of the east coast could close down this gap further, but STILL I imagine the east coast gang MUCH prefers to hit fields where "something went on". Eg.: a tavern, a stage stop, a cellar hole, etc..... Not just "random cultivated fields" in our relatively new country.
