The idea behind a smart beta ETF is to provide investors with an effective way to gain exposure to diverse systematic factors such as growth, volatility, dividend payments, or so-called momentum investing. Momentum investing tries to capitalize on existing trends within the market that will continue into the future. The theory behind this is that an established trend has a greater tendency to follow its existing path rather than to change its direction. (For more, see: Momentum Investing.) Here are the top five smart beta momentum ETFs in terms of current assets under management according to ETF.com (2016)

MTUM - iShares Edge MSCI USA Momentum Factor ETF

According to BlackRock (2016), MTUM provides investors access to mid- and large-cap stocks within the US that exhibit a generally higher price momentum than most security offerings. Launch date of this US-domiciled fund was Apr. 18, 2016. As of Aug. 29, 2016, it has a total asset volume of around $1,758 million. MTUM ETF comes with an expense ratio of .15%. As of Jul. 31, 2016, MTUM shows an annualized total return of 14.89% since its inception.

PDP - Invesco DWA Momentum ETF

PDP features an expense ratio of .63% and attempts to produce investment results that generally match those of the so-called DWA Technical Leaders Index. Managed by Mr. Peter Hubbard from Invesco Capital Management LLC, this fund was issued on Mar. 1, 2007. It encompasses an AUM of ca. $1,437 million, as of Aug. 29, 2016. Since its launch, PDP features an annual average performance of 6.82% as of Jul. 31, 2016.

ONEO - SPDR Russell 1000 Momentum Focus ETF

As the name suggests, ONEO’s primary target benchmark is the Russell 1000 Momentum Focused Factor Index. The ETF is overseen by SSGA Funds Management and entails an expense ratio of .20%. The fund comes with a large-cap equity focus and as of Aug. 29, 2016, has total assets of around $361 million. The inception date of ONEO was last year on Dec. 03, 2015. ONEO's average annual performance since inception is 6.81% as of Jul. 31, 2016.

PTH - Invesco DWA Healthcare Momentum Portfolio

As described by Invesco (2016), PTH’s primary benchmark is the so-called Dorsey Wright’s Healthcare Technical Leaders Index. The ETF typically has approximately 90% of its assets invested into this index’s common stocks. The goal of this particular index is to track among others health care equipment and supplies companies, health care providers and services corporations as well as biotech firms that exhibit strong momentum. PTH has an expense ratio of .60% and was issued on Oct. 12, 2006. As of Aug. 29, 2016, PTH comprises an asset volume of about $69.85 million. Since its launch in October 2006, PTH has an annual average performance of 7.82% as of Jul. 31, 2016.

PRN - Invesco DWA Industrials Momentum Portfolio

This is another smart beta momentum ETF, managed by Invesco Capital Management LLC. PRN attempts to produce for its investors results that match the yield/price of DWA Industrials Technical Leaders Index. This index specifically examines companies in many areas including stock valuation, fundamental growth, risk, and the timeliness of the investment offering. It has an expense ratio of .60%, an AUM of $44.60 million (as of Aug. 29, 2016) and was launched on Oct. 12, 2006 (just like the above-mentioned PTH ETF). Since the inception, PRN features an annualized total return of 7.84%.