Demand for safe-haven assets peaked amid an uncertain global economic outlook and growing volatility across many asset classes. U.S. treasury bonds benefited from this trend as yields on 10-year Treasury notes have fallen by almost 50 bps to 1.79% (as of April 12, 2016) so far this year, leading Treasury valuation to soar (read: Time for These Buy-Ranked Treasury Bond ETFs). Treasury ETFs have lately gained in popularity as investors look to protect their portfolio and search for stable yields in this ultralow rate interest environment. The turbulence in the economy led the central bank to lower the number of hikes and the federal funds rate this year. It now expects the federal funds rate to rise to 0.875% by the end of the year, instead of the previously expected 1.375%, implying only two rate hikes as compared to the four projected in December. Last month, the Fed Chair Janet Yellen stated that the U.S. central bank should proceed cautiously in adjusting policy rates (read: ETF Winners & Losers Following Yellen Comments). Yellen’s comments were further reinforced by Fed Bank of New York President William C. Dudley who said that due to the uncertain outlook on the U.S. economy, a cautious and gradual approach to interest rate increases is expected. In fact, John Brynjolfsson, the chief investment officer of Armored Wolf, sees bond yield staying low in the short term, which could even go a bit lower. In March, the European Central Bank (ECB) came up with a more intensified economic stimulus, opting for multiple rate cuts and the expansion of its quantitative easing program to boost the economy. Monthly asset purchases were raised to EUR 80 billion from EUR 60 billion previously. Easy monetary policy globally, a delayed rate hike in the U.S. and continued volatility in the global markets have made treasury securities a winner. As investors scurry to safer assets, we highlight five Treasury bond ETFs that have posted encouraging returns so far this year. These products also have a bullish Zacks ETF Rank #2 or ‘Buy’ rating (see: all Government Bond ETFs here). PIMCO 25+ Year Zero Coupon U.S. Treasury Index Fund (ZROZ) This ETF tracks the BofA Merrill Lynch Long US Treasury Principal STRIPS Index. The product holds 20 securities in its basket. Both the effective maturity and effective duration of the fund is 27.42 years. This fund has AUM of $253.4 million and trades in average volume of 39,000 shares. The product charges 16 bps in annual fees and returned 13.6% in the year-to-date period (as of April 12, 2016). The fund yields 2.00% annually. Vanguard Extended Duration Treasury ETF (EDV) EDV tracks the Barclays U.S. Treasury STRIPS 20–30 Year Equal Par Bond Index. This particular 74-bond basket has an average effective maturity of 25.2 years. The effective duration of the ETF stands at 24.8 years. The fund has amassed about $529.7 million in assets and trades in average volume of 74,000 shares. Investors should also note that this is a cheap product, as it charges just 10 basis points a year, so it will be a very low cost way to get into long duration bonds. The fund yields 2.64% annually. The fund was up 13.2% in the year-to-date period (as April 12, 2016). iShares 20+ Year Treasury Bond ETF (TLT) This is one of the most popular and liquid ETFs in the long-dated bond space with AUM of over $8.1 billion and average daily volume of more than 8.5 million shares. It tracks the ICE U.S. Treasury 20+ Year Bond Index, holding 32 securities in its basket. The fund has average maturity of 26.6 years and effective duration of 17.8 years. It charges 15 bps in annual fees and is up 9% in the year-to-date period. The fund yields 2.35% annually (read: ETFs to Gain or Lose After Strong Jobs Report). Vanguard Long-Term Government Bond ETF (VGLT) The fund with AUM of $324.7 million invests in 70 U.S. government bonds. The average effective maturity of the fund is 24.9 years while the average duration of the fund is 17.7 years. The fund charges 10 bps in fees. The fund has average daily volume of more than 85,000 shares. The fund yields 2.52% annually. The fund advanced 8.7% so far this year. SPDR Barclays Capital Long Term Treasury ETF (TLO) The fund tracks the Barclays Long U.S. Treasury Index. This particular 46 bond fund has an average effective maturity of 25.2 years. The modified adjusted duration of the ETF stands at 17.97 years. The fund has amassed about $608 million in assets and trades in average volume of 146,000 shares. It charges just 10 basis points a year. The fund yields 2.18% annually. The fund was up 8.5% in the year-to-date period (as April 12, 2016). Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report >> Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report PIMCO-25Y ZERO (ZROZ): ETF Research Reports VANGD-EX DUR TR (EDV): ETF Research Reports ISHARS-20+YTB (TLT): ETF Research Reports VANGD-LT GOV BD (VGLT): ETF Research Reports SPDR-BC LT TRS (TLO): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report