Learn Icelandic: Það er mikilvægt að kortleggja velstæða. - It is important to map out the well-off.

Velstæða is the masculine plural accusative form of the adjective velstæður (well-off). In Icelandic, you can drop the noun (like "fólk") and use a plural adjective on its own to refer to a demographic group. When referring to a mixed group of people, the masculine plural is the default. It is in the accusative case here because it is the direct object of the verb kortleggja.

Why is the adjective mikilvægt in the neuter singular form?

The adjective mikilvægt (important) describes the action of the sentence. The true grammatical subject here is the entire infinitive phrase að kortleggja velstæða (to map out the well-off). In Icelandic, infinitive phrases are treated as neuter singular, so the base adjective mikilvægur takes the neuter singular form mikilvægt.

Is kortleggja used for literal maps, or is it a metaphor here?

It is a compound of kort (map) and leggja (to lay or put). While it can mean making a physical map, it is frequently used metaphorically—just like "to map out" in English—to mean surveying, identifying, or getting a thorough overview of a demographic or situation.

How is the adjective velstæður constructed?

It is formed from the adverb vel (well) and the adjective stæður (standing or situated). It translates perfectly to the English concept of being "well-off" or financially secure.