July 27 (Reuters) - Global exchange-traded funds (ETFs) have attracted record investments this year, driven by a rally in equities, low interest rates and ample cheap cash. According to Refinitiv data, global ETFs received a combined inflow of $639.8 billion in the first half of this year, more than double the same period last year. Equity ETFs secured $490.65 billion or 76% of the total inflows, while bond ETFs received $136.6 billion. Analysts said the rising interest in ETFs was due to their better tax efficiency, transparency and higher returns over actively managed mutual funds. Global mutual funds saw a combined inflow of $922 billion in the first half of the year, which was just a 2% increase. "ETFs have become the investment vehicle of choice for a larger number of investors. They faced their toughest test ever in early 2020 and passed with flying colors," said Ben Johnson, director of global ETF research at Morningstar, based in Chicago. "Investors who might have been concerned about how ETFs would hold up during stress periods may have become new ETF converts over the past year or so." The data showed U.S. ETFs attracted the bulk of the money, with inflows of $469.3 billion, while European and Asian ETFs received $106.8 billion and $38.3 billion respectively. Some analysts said the bigger inflows into the United States was due to better economic recovery hopes, with more people vaccinated in the United States compared with other regions. The success of ETFs has also prompted fund houses to launch more ETFs this year and some to convert their existing mutual funds into ETFs. According to Refinitiv data, 709 ETFs have been launched so far this year, compared with just 428 in the same period in 2020. Last month, Dimensional Fund converted four of its mutual funds into ETFs, while Guinness Atkinson Funds turned two of its funds into ETFs in March. Active ETFs, which aim to beat the broader index unlike passive ETFs which follow the index, secured $65.4 billion worth of inflows in the first half, a 161% rise from last year. "Active ETFs have been taking advantage of investors" desire to better slice and dice the market place into subsectors that have appeal," said Elliot Herman, chief investment officer at PRW Wealth Management, based in Massachusetts. "Examples include innovation, cannabis, ESG (environmental, social and governance), and many others." The Vanguard 500 Index Fund and Vanguard Total Stock Market Index Fund led this year"s ETF inflows, receiving over $20 billion in the first half of this year. The iShares Core S&P 500 ETF secured inflows worth a net $12.6 billion.