Complex sentence: The island's population peaked at 1,738, in 1948, and has been in a steady decline since, due chiefly to emigration; the number of people who emigrated from the island since the 1950s exceeds its current population.
Split into simpler sentences: The island's population peaked at 1,738, in 1948, and has been in a steady decline since, due chiefly to emigration. The number of people who emigrated from the island since the 1950s exceeds its current population.