My guess is descending, but I want to have some theoretical background. I was using an application and my intuition told me to click the scroll bar down just to find previous years, and I felt surprised when I was wondering around the 2020s...
Choice restriction for data not having sense in this task quite enough also isn't present sense to change an order, it can create a small embarrassment with changing chronology ordering model, for example month sorted from DEC to JAN.
I can't tell precisely what such as tasks more in your case, drawing up of reports or forecasts. Therefore value by default left reports as for their construction there are necessary data for last years.
And one more...
If to take into consideration typical temporary model of interaction with documents - I don't see sense in formation of reports older than 5 years, and forecasting for 10 years forward are more senior. Documents of five years' prescription already most likely are in archive, and information received from the report hardly will carry any practical sense, except the publication on a company website in the section history of company .
Also illogically the forecast of this passenger traffic of railway transport in 2050 based on data for 1901 looks.
The chronology of a choice will remain with a scroll direction if you limit a choice of values not having sense for various type of documents.
Owing to that the greatest number of inquiries will be in a range of 3-5 years, it is possible to limit number of years in the list. For example if your company is based in 1997 - report creation for 1980 has no logic sense, otherwise the quantity of similar inquiries is insignificant a little.
More detailed info or wireframes simplify decision search, but, I hope that correctly understood your task.
In general it is always descending. But for forecast, it is best to use ascending. Simply because forecast always means future, so always have date from now to the future. If you see weather forecast it is also ascending link.
If you look at the stock market, it always shows dates in ascending order.
If you think of 2020, I would suggest instead of giving long list of years, just present current 3 years; for the rest, let the visitor manually choose it by typing or from archive!
The most important thing is that the years are sorted and the sorting is consistent through your design.
I think that the direction of the sorting should depend on which years are more frequently used - the older years or the newer ones.