Earlier this year, Dow component UnitedHealth (NYSE: UNH), IHF’s largest holding at a weight of 13.9%, agreed to acquire Catamaran for $12.8 billion in cash.

In 2009, Express Scripts (NasdaqGM: ESRX) spent $4.7 billion to acquire WellPoint and followed up that deal with the $29 billion acquisition of Medco in 2012. [Healthcare ETFs Remain Sturdy]

Last year, Morgan Stanley identified Express Scripts, Cigna and Aetna as possible takeover targets. Investors like the IHF story. A year ago, IHF had about $400 million in assets under management, meaning the ETF’s AUM total has more than doubled in a year.

iShares U.S. Healthcare Providers ETF