Learn Swedish: Eftersom värdet sjunkit, måste vi utvärdera budgeten. - Because the value has dropped, we must evaluate the budget.

This is a common feature in written Swedish called 'ha-bortfall' (dropping the 'ha' verb). In a subordinate clause, like the one starting with Eftersom, you are allowed to drop the auxiliary verbs har and hade. The meaning stays exactly the same as if you had written Eftersom värdet har sjunkit.

Why is it måste vi and not vi måste after the comma?

This happens because of the V2 (verb-second) rule. The entire subordinate clause Eftersom värdet sjunkit takes up the first position in the sentence. To keep the main verb in the second position, måste has to come before the subject vi.

What is the base form of the verb sjunkit?

The infinitive is att sjunka (to sink, drop, or fall). The form sjunkit is the supine form. You always use the supine form when a verb belongs to har or hade, even when that helper verb is left out like it is here.

I see the word värde in both halves of the sentence. Are they related?

Yes! värdet means 'the value'. In the second half, the verb utvärdera (to evaluate) is built from the prefix ut- (out) and värdera (to value or appraise).