This is from a news article.
Consumer prices were up 4.2 percent in March from a year earlier, according to the Fed’s preferred measure of inflation, the Personal Consumption Expenditures index, the Commerce Department said Friday.
I looked up 'up' in the Merriam-Webster dictionary.
adverb 3d. : to or at a greater speed, rate, or amount
adjective 2b : being above a former or normal level (as of quantity or intensity)
I think here 'up' might be an adverb if 'were' is an intransitive complete verb and an adjective if 'were', a linking verb.
I wonder what part of speech 'up' is in the above quote.