If you ask your typical long-only investor (or financial advisor) how momentum is doing this year they’ll likely say, “Amazing!”

This statement will almost surely be based on the fact they own (or know about) the iShares “Momentum Factor” Fund (Ticker: MTUM). MTUM is on fire year to date (through 5/31/2017):(1) 17.42% based on market prices versus 8.66% for the S&P 500 Total Return Index.

Not too shabby–Perhaps Eugene Fama and Ken French labeled momentum, “The premier anomaly,” for good reason!

But is MTUM a good representative of the momentum factor?

This is where the analysis gets confusing if one is trying to capture the classic academic momentum anomaly, which is associated with sorting the cumulative return over the past year, skipping the most recent month. Long story short, MTUM’s short-run performance doesn’t resemble anything that looks like momentum to an academic researcher.

First, the academic long/short momentum factor, as per Ken French’s website data, is down 1.70% through 5/31/17 (attempts to control for size effects).

Where to get the data for long-only momentum factor long/short portfolios

So from a professional academic researcher prospective, momentum is actually sucking wind this year.

But MTUM is long-only and long/short factors can be confusing. Also, the vast majority of investors don’t invest in long/short factors, they invest in long-only factor portfolios. Let’s make this analysis simpler and focus on long-only momentum portfolios. We can refer back to Ken French’s data website and examine the YTD performance of long-only academic momentum decile portfolios, or portfolios of stocks sorted on the classic “2-12” price momentum measure.

Where to get the data for long-only momentum decile portfolios

For the year, the market-cap weighted (or “value-weighted”) top decile momentum portfolio (“FF_MOM_VW”) is up 7.52% through 5/31/17, and the equal-weight top decile momentum portfolio (“FF_MOM_EW”) is up 0.49% through 5/31/17. The S&P 500 TR Index over the same period is up 8.66% while the S&P 500 EW TR Index is up 6.77%.