Fidelity has also asserted itself as a legitimate player in the sector ETF arena. The mutual fund giant launched 10 sector ETFs backed by MSCI indices last October. Today, the suite has over $1 billion in combined assets under management and five of those ETFs have over $100 million in AUM. [ETFs With MSCI Indices Prove Popular]

Issuers of alternatively-indexed industry and sector ETFs are also benefiting. For example, of the top 35 ETFs issued by PowerShares, the fourth-largest ETF issuer, in terms of 2014 inflows, nine are sector or industry funds, according to issuer data.

That group includes the PowerShares Dynamic Pharmaceuticals Portfolio (NYSEArca: PJP) and the PowerShares Dynamic Food & Beverage Portfolio (NYSEArca: PBJ).

First Trust has become one of the fastest-growing U.S. issuers due in part to its AlphaDEX lineup of sector funds. At the end of last year, First Trust was the ninth-largest U.S. ETF issuer with $19.7 billion in AUM. The company is now the sixth-largest sponsor with over $28 billion in AUM.

As just three examples, the First Trust Consumer Staples AlphaDEX Fund (NYSEArca: FXG), First Trust Health Care AlphaDEX Fund (NYSEArca: FXH) and the First Trust Energy AlphaDEX Fund (NYSEArca: FXN) have combined to add over $1 billion in new assets. [AlphaDEX ETFs Drive First Trust’s Growth]

Tom Lydon’s clients own shares of SPY.