The United States Oil Fund (NYSEArca: USO), which tracks West Texas Intermediate crude oil futures, came into Wednesday with a year-to-date gain of nearly 14% as oil prices recently ascended to multi-year highs. However, there are some data points oil bulls should not ignore regarding USO’s near-term health.

The expanding global economy has increased demand for commodities and drawn down oil inventories. For instance, according to the Energy Information Administration, U.S. crude stockpiles have declined for the past 10 consecutive weeks and are now at their lowest level since 2015.

Investors may want to have a look at recent options activity in USO.

“We’re talking about the 10-day moving average of USO’s put/call skew on 5% out-of-the-money (OOTM) options. Readings for out-of-the-money puts against that of their call counterparts — fell to nearly 1.0 last week. This was the lowest such reading since the June 2014 peak in oil prices, marking a dramatic drop from nearly four-year highs earlier this year,” according to Schaeffer’s Investment Research.

What’s Next for Oil?

Fortunately, historical data suggest the aforementioned options activity in USO, when it occurs, can be a bullish signal over the near-term, but more bearish as the months pass by.