As far as I understand, when we calculate GDP we want to estimate wealth produced during given year in given country. But it seems like it will be problematic when using the income approach (the expenditures approach doesn't suffer from this problem. After all, in the vast majority of cases people pay full price for services and goods at one sitting. When they have problem with paying full price they take a loan and then pay full price with money that they got from a creditor).
1.We include income from receiving interest because giving loans is a service. But if lending money is a service, then it can viewed as kind of service what you can spend literally years to pay for. There will be incomes from some loans that were given in previous years, yet they they will by included in GDP of this year.
2.We include deprecation. It seems to make sense at first. After all, if an asset was produced this year and was completely worn out the same year, then it's still production. By including deprecation we avoid situation when worn out asset is treated like it has never been produced in the first place. BUT, assets that were created in previous year are also included in this calculation. Why would we include cost of deprecation of something that was NOT produced this year?
Or maybe I don't understand something and there are good reasons to make exceptions for interest and deprecation?
P.S. Okay, so we add deprecation in order to ignore it altogether, thus we don't really count deprecation of old assets. But how about income from loans given years ago?