Count baby boomers and millennials among the groups of investors that are flocking to exchange traded funds.

TD Ameritrade (NasdaqGS: AMTD) recently examined the growth of exchange-traded funds (ETFs) and how the Company’s clients are using them in their portfolios. The findings illustrate the shift in investment trends between 2012 and 2014 for millennials, boomers and retirees, according to the brokerage firm.

Of ETF assets held at TD Ameritrade, 13.6% are held by those in the 26 to 35 age group, or millennials. The 56 to 65, 66 to 75 and 76 and above age demographics, which include baby boomers and retirees, combine for over 17.2% of ETF assets held at TD Ameritrade. [Millennials Crimp These ETFs]

“ETFs have surpassed the growth rate of mutual funds over the past 13 years, mainly due to their ease of use and millennials choosing to allocate more and more of their portfolios to ETFs,” said Alex Teyf, Director, Mutual Funds and ETFs at TD Ameritrade.

Since 2012, investors across all age groups lowered exposure to international ETFs with boomers, millennials and Gen X doing so to the tune of 2%, according to TD Ameritrade data. Those in the 66 to 75 group pared international ETF exposure by 4%. Likewise, all age demographics have been leaving commodities, with the largest departures coming courtesy of older investors. Those in the 56 to 65, 66 to 75 and above 76 age brackets trimmed their commodities ETF exposure by an average of almost 12%.

With the dollar surging and emerging markets rebounding somewhat this year, outflows from international ETFs have stemmed with investors flocking to ex-U.S. developed market funds. ETFs added $18.3 billion in new assets last month, with the bulk of those flows going to EAFE and Japan funds. Seven of this year’s top 10 asset-gathering ETFs are international developed market funds. [International ETFs Lead May ETF Flows]

At the sector level, TD Ameritrade notes healthcare allocations grew the most since 2012. Interestingly, that growth has been fueled by old investors. The aging U.S. population is widely cited as validation of the long-term bull thesis for healthcare stocks and ETFs. According to TD Ameritrade data, investors in the 56 to 65 age group and those 76 years old and older boosted healthcare allocations by 3% while investors ages 66 to 75 increased their healthcare exposure by 4%. [More Upside Seen for a big Healthcare ETF]

Over the past three years, the Health Care Select Sector SPDR (NYSEArca: XLV), the largest healthcare ETF by assets, has surged more than 117% while hauling in $4.21 billion in assets.

Chart Courtesy: TD Ameritrade