A lot of people put a great deal of stock on the age of a whiskey. The older it is the better it is or so they think. Problem is it ain't necesssarily so, or that chronological years mean a lot of different thing depending on the type of whisky (or any other type of spirit ). That is why I refer to Bourbon in this article as the short attention span whisky. It takes a lot less time to age a bourbon.
To steal some concepts from Einstien's theories of time and relativity, time is not absolute but relative. In these cases however they are due to more mundane enviromental factors than his theories.When one thinks about the age of a spirit you must think of the aging factors to be able to compare the chronological vs relative ages between them.
Bourbon is aged in fresly charred oak barrels in Kentucky. Scotch is aged in used barrels in Scotland . Kentucky has a much wider (and higher) temperature range during the aging process and the warehouses are subject to wider temperature swings due to their construction (mostly wood, although in a few cases metal and heated in the winter leading to very rapid aging). This and the fresh char causes the bourbon to age at what I would guess to be about twice the rate of scotch whisky. Unfortunately it also evaporates at a much higher rate for many of the same reasons but that is beside the point.
Bourbon ages quite fast and many bourbons top out at 10-14 years of age. There are a few exceptions to this Hirsch 16 and 20 year old bourbons are a good example. They,however, are not from Kentucky but from central Pennsylvania, a more moderate climate. There are few bourbons from Kentucky that have lasted as long . Those that have were usually in the coldest or at least most constant parts of the warehouse (or rackhouse) and are small in number.
In Scotland however due to the colder climate, higher humidity and construction of warehouses (thick stone or brick walls for the most part) coupled with used barrels lead to a longer aging process to achieve the same type of aging or should I say for the whisky to achieve the same point in its development. So when you talk about how old a spirit is you must consider it within its own aging framework. Somewhat like dog years versus human years (no reflection meant on the bourbon by that example).
This has led to some interesting conundrums . Because bourbon is not as highly regarded as Scotch and further because of the age discrimination that bourbon has against it , bourbon is quite cheap compared to scotch even though there are some outstanding bourbons out there.
The same can also be generally applied to American Rye Whiskey (what little there is anymore).