Simply put, there's no shortage of emerging markets ETFs on the market today. There are large-cap and small-cap funds that track multiple countries within one fund and there are scores of country-specific funds offering exposure to both cap spectrums.

Both segments have gotten off to fine starts this year as the Vanguard MSCI Emerging Markets ETF (NYSE: EWO) was up almost 12% before today and the SPDR S&P Emerging Markets Small Cap ETF (NYSE: EWX) was up slightly more than that.

But what about mid-caps? Those that aren't emerging markets junkies may have forgotten about the IndexIQ Emerging Markets Mid Cap ETF (NYSE: EMER), which debutted in July and is the only multi-country emerging markets ETF devoted exclusively to mid-caps on the market today. There is a mid-cap ETF for Brazil, the Global X Brazil Mid-Cap ETF (NYSE: BRAZ).

Thinly traded (volume is about 1,300 shares per day), the IndexIQ Emerging Markets Mid Cap ETF has attracted about $1.5 milion in assets under management since its debut. Those numbers speak to the ETF's under-the-radar status, but is it reasonable to call EMER a hidden gem?

With an expense ratio of 0.75%, EMER is home to 200 stocks across 10 secors. Four of those sectors – consumer discreationary, financials, industrials and materials – receive double-digit allocations. Seventeen countries are represented in EMER with three – Taiwan, South Africa and South Korea – accounting for about 52% of the fund's country weight. At the bottom of spectrum, Hungary, Egypt and Russia combine for just 1.2% of EMER's weight.

The sizable allocation to Taiwan and South Korea has been done before. Almost too much when it comes to multi-country emerging markets ETFs. Taiwan and South Korea dominating and emerging markets ETF is so 42 seconds ago and in the case of a new ETF like EMER, it should be doing something to set itself apart.

Actually, the ETF is doing that and doing it with performance. Year-to-date, EMER as outperformed VWO and is barely lagging EWX, but no one is talking about that. In fact, we'd venture to say EMER might be the best of the trio if its allocations to China, Brazil, India, Thailand and Indonesia were higher.

And if you're looking to break a tie among emerging market mid-cap ETFs, EMER and the Global X Brazil Mid Cap ETF have moved in lockstep with each other this year, so breaking the tie will have to come at a later date.

If nothing else, EM mid-cap ETFs such as BRAZ and EMER are worth a look to diversify the emerging markets portion of a portfolio across all cap ranges. And hey, those ETFs are doing better than VWO this year.

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