Back in the day - a singer would get a gold record for selling a million copies. How accurate were the counts, and how did they count? Did the record companies produce some kind of certified list of the number of copies of each title produced, and/or the number of copies shipped to stores (or whatever)? Sure - you could produce (or claim you produced) a million copies, with only part of that million actually being shipped and sold (without being returned). Also - it could take years - even decades - to reach the million mark. Is someone still keeping an accurate count of copies sold/streamed/downloaded?
I can’t answer of how they count, but I do know that they keep track for a long time. I’ve heard about albums awarded gold or platinum decades after they were released.
I would find it weird if record companies didn’t have accurate (to a surprising degree) records of the records being sold. It is their business, after all.
The number of copies produced wouldn’t mean a thing, as stuff sitting in warehouses (and ending up in a dump some day) is not sales.
The award was launched in 1958; originally, the requirement for a Gold single was one million units sold and a Gold album represented $1 million in sales (at wholesale value, around a third of the list price). In 1975, the additional requirement of 500,000 units sold was added for Gold albums.
It’s probably always been a kind of easy thing to get retailers to report back the sales figures- it benefits everyone to know what’s selling and in what quantity. Maybe it wasn’t quite so immediate in pre-computer, pre-internet days, but I don’t doubt that record stores had a very keen interest in knowing what records were and weren’t selling, and passing that information upward didn’t do anything negative for them- they’d be able to get more to sell, and reinforce the idea that this or that act should have a tour, second album, etc…