Complex sentence: Their population declined by more than 50% between 1997 and 2003; despite the small rebound in their numbers since then, they have been surpassed in size by the rapidly growing Korean communities in Australia, New Zealand, the United Kingdom, and southeast Asia.
Split into simpler sentences: Their population declined by more than 50% between 1997 and 2003. Despite the small rebound in their numbers since then, they have been surpassed in size by the rapidly growing Korean communities in Australia, New Zealand, the United Kingdom, and southeast Asia.