Questions & Answers about Kysyntä oli huono aiempiin vuosiin verrattuna.
Why do aiempiin and vuosiin end in -iin?
This is because of the postposition verrattuna (compared to). When you use verrattuna, the thing you are comparing to must be in the illative case. Since we are talking about "earlier years" in the plural, both the adjective and the noun take the plural illative ending -iin.
What exactly is the word verrattuna grammatically?
It comes from the verb verrata (to compare). It is the passive past participle (the TU-participle, verrattu) put into the essive case (-na). Literally, it translates to "as having been compared."
Where does the word aiempiin come from?
It is the plural illative form of aiempi (earlier), which is a comparative form of the adjective aikainen (early). You will also often see the alternative comparative form aikaisempi, which would become aikaisempiin in this sentence.
Why is huono in the nominative case instead of the partitive huonoa?
Abstract nouns like kysyntä (demand) often take a partitive adjective (huonoa) because they represent an uncountable concept. However, using the nominative (huono) is also perfectly correct here; it simply treats the demand of that specific period as one complete, defined entity.