Why are more and more hospitals partnering with each other?

Since I began working at the Puget Sound Business Journal about two months ago, I've noticed nearly every other week there's a new hospital affiliation — or partnership, or agreement, or some term indicating two organizations are joining forces — announced by a major health care company in the area. Just since I've been here, Monroe Valley General Hospital has become a part of EvergreenHealth, Group Health has moved some of its services to Swedish Medical Center and Yakima Valley Hospital joined Virginia Mason's network. In recent years, some of the biggest news in the hospital world was Swedish's new affiliation with Providence Health & Services.