As the emphasis on the effect of investment fees on retirement outcomes and new regulations for fiduciary responsibility for 401(k) fee reporting has increased, index funds and ETFs, marketed for their low fees, have become increasingly popular.   According to an article in the Wall Street Journal, increased demand has inspired the creation of new index funds and ETFs.   However, some of these funds have become specialized, restrictively defining the markets that they are tracking, which may increase the expense of the fund and unwittingly limit the diversity of your investment portfolio.  Before selecting an ETF, make sure you know the actual fee ratio associated with the fund, what your risk versus reward tolerability is, and how the fund will affect the makeup of your portfolio.