A year ago, solar energy and Japan exchange-traded funds roared back after suffering near-death experiences. At 2014's halfway mark, ETFs focused on India, coffee and gold miners are the comeback kids.

Among the leaders in those sectors are the Market Vectors India Small Cap Index (SCIF), up 61 percent as of June 27, and the iPath Dow Jones-UBS Coffee Total Return Sub-Index ETN (JO), up 53 percent. Last year SCIF was down 29 percent, and JO fell 32 percent. Another top performer is Global X Gold Explorers ETF (GLDX), up 40 percent this year after plummeting 62 percent in 2013.

One of the year's most unexpected twists is that the best-performing bond ETF was one holding long-term Treasury bonds, an ETF that is more sensitive to rising interest rates than any other bond ETF. You would have been considered kind of crazy if you had bought it at the start of the year, when conventional wisdom said rates were going to rise. Instead, rates fell and the Pimco 25+ Year Zero Coupon US Treasury Index ETF (ZROZ) rose 22 percent. Credit for a timely contrarian call goes to Paul Baiocchi, a former analyst for etf.com, who predicted lower rates and, after putting ZROZ in his 2014 picks, was promptly mocked by his colleagues.

Vanguard's Flow-Getter

Among ETF issuers, Vanguard Group Inc. had a great first half. The firm took in $31 billion -- 42 percent of the $71 billion industry total. In addition, 64 of its 67 ETFs attracted new money, an average of $460 million per fund. In contrast, BlackRock Inc., the No. 2 in first-half flows with $26 billion, saw its average ETF take in $70 million.

Vanguard also had six ETFs in the top 10 list, including the overall No. 1 flow-getter, the $4 billion Vanguard FTSE Developed Market ETF (VEA). It tracks 1,300 international developed stocks for a fee of 0.09 percent of assets annually.

Vanguard's rule of the top 10 list was a sign that the short-term money pulled back after last year's run -- buy-and-hold investors tend to buy Vanguard's ETFs. Many of the favorite super-liquid ETFs of quick-buck traders were on the top 10 list of ETFs seeing outflows. That includes SPDR S&P 500 Trust (SPY), which lost $14 billion; PowerShares QQQ Trust (QQQ), which lost $4 billion and iShares Russell 2000 ETF (IWM), which lost $2.3 billion. However, money moved into many of these ETFs in June.

Related story: BlackRock Retakes Lead in ETF Sales in Second Quarter on Emerging Markets

First Trust, which offers smart-beta ETFs popular with retail investors, also had strong inflows. Some $5 billion poured into its ETFs, which makes it the overall No. 3. A popular fund in its stable is the First Trust Europe AlphaDEX Fund (FEP). It uses both growth and value fundamentals to score and weight its portfolio. FEP took in $450 million, about doubling its size to just under $1 billion. Along with First Trust, more than 15 ETF issuers had inflows that represented at least a 20 percent jump in assets.

New Momentum Play

The first half was a fertile time for the ETF industry, and the 1,600 existing ETFs were joined by 99 new ones. That compares with 72 new launches as of last year's midpoint. There were also 23 closures so far in 2014, well below the 42 a year ago.

The strategy mix of the ETFs ranged from plain vanilla indexing to fairly complex financial wonkery (such as factor-based smart-beta techniques). The most successful launch in terms of assets is a momentum strategy ETF called the First Trust Dorsey, Wright Focus Five Fund (FV). The $325 million ETF basically invests in the five of its sector momentum ETFs that exhibit the most momentum and relative strength in price. Basically, momentum funds invest in areas going up relative to the market, and try to ride the wave.

What to expect in the second half? We'll see the first-ever credit default swap ETFs. And non-transparent actively managed ETFs look likely to win approval by the Securities and Exchange Commission. That would open the floodgates for giant mutual fund firms to launch more actively managed ETFs. That's because the ETFs wouldn't have to show the world their holdings -- be transparent -- every day, which was a major concern of the firms.

Last but not least may be the launch of the Winklevoss Bitcoin Trust ETF, which could add a nice bit of circus sideshow to the second half. Stay tuned. It’s going to get interesting.

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Eric Balchunas is an exchange-traded-fund analyst at Bloomberg. More ETF data is available here, and weekly ETF podcasts can be found here.