Big dreams, but okay. Depends on industry and your capability. But usually job hopping is between 15% (if you're already in higher management) to 20%. If you're good/ lucky, or had been severely underpaid in the past - perhaps up to 30%. I hardly see more than 30% but then again, I'm not in HR. HR-ians would likely be more privy to such information.

Either the guy was severely underpaid last time, or he upgraded real good and fast, or headed to other countries (with better currency, or offer). Either way, I'm on the side of being a realism with average benchmark.