Question

Use Strunk’s advice to make the second half of the sentence parallel.

“the economy had changed, there were shifts in the population, and the war ended”

“the economy had changed, and there were shifts in the population, and the war had ended”

“the economy had changed, the population had shifted, and the war had ended”

Answer 1

Use the same grammatical form for each item. The third sentence is correct:

"the economy had changed, the population had shifted, and the war had ended."

Even better (more concise, per Strunk):

"the economy changed, the population shifted, and the war ended."