Many niche ETFs have only a few million dollars in assets under management — asset size can have a big impact on an ETF's ability to track an index and trade efficiently. (cnbc.com)
That assumption is probably more than adequate to cover the expenses of investing in these asset classes through mutual funds or exchange - traded funds. (paulmerriman.com)
I would say that they should definitely have exposure to stocks, but only as in their asset allocation as they can emotionally tolerate without losing sleep! (barbarafriedbergpersonalfinance.com)