By multiple metrics, cruise company Carnival (CCL 0.29%) (CUK 0.19%) had a great year in its fiscal 2023 (ended in November). The company had all-time high revenue of $21.6 billion. And based on its current record bookings, fiscal 2024 is shaping up nicely as well.However, I believe that there's an important Carnival metric that's been completely overlooked and underappreciated by investors: The company introduced 3.5 million people to cruises last year, and this might be the key to reaching management's fi ...