e.g. some physical products will be disposed of when they have degraded to the extent that it does not make economic sense to repair them, or for someone else buy and reuse/repair them, given the costs of doing so compared to e.g. just buying a comparable new item or a comparable used item in better condition. so they cost a lot to buy in the first place, but now they roughly zero value, or perhaps a very low value as scrap.
That said, some other perfectly good stuff (with relatively high re-use value or scrap value) will be thrown away.
Why do you want to estimate this number? If you have a particular use in mind, it might be possible to come up with a more relevant and useful statistic.
e.g. some physical products will be disposed of when they have degraded to the extent that it does not make economic sense to repair them, or for someone else buy and reuse/repair them, given the costs of doing so compared to e.g. just buying a comparable new item or a comparable used item in better condition. so they cost a lot to buy in the first place, but now they roughly zero value, or perhaps a very low value as scrap.
That said, some other perfectly good stuff (with relatively high re-use value or scrap value) will be thrown away.
Why do you want to estimate this number? If you have a particular use in mind, it might be possible to come up with a more relevant and useful statistic.