Complex sentence: It is estimated that there are as few as 5,000-10,000 or as many as 25,000 virtual assistants worldwide; the profession is growing in centralized economies with "fly-in, fly-out" staffing practices.
Split into simpler sentences: It is estimated that there are as few as 5,000-10,000 or as many as 25,000 virtual assistants worldwide. The profession is growing in centralized economies with "fly-in, fly-out" staffing practices.