The number of oil traders betting on $100-per-barrel WTI by 2019 has surged in the past week, Reuters reported.

Open positions on $100 December 2019 WTI call options have increased 30% in the past seven days to reach a record 31,000 lots.

A three-figure WTI price previously seemed unlikely due to record US production growth and relatively flat global demand. However, the upcoming oil sanctions on Iran, together with bottlenecks preventing US oil from reaching the market, saw the price hit fresh four-year high of $76.41 on October 3.

The moves suggest that traders are becoming increasingly skeptical that supply from other nations will be enough to compensate for the loss of Iranian crude from the market, when US sanctions are restored on November 4.

“Over the last two weeks, there’s been a lot more evidence that even some of the larger customers – India and China – are not going to be buying Iranian crude from November,” John Saucer, vice president of research and analysis at Mobius Risk Group said.

“These sanctions are likely to be a lot more effective than people even thought,” he added.

Iranian oil exports have fallen by 800,000 barrels per day (b/d) to 2 million b/d since April, the Institute of International Finance said.

Speculation on the total impact on Iranian oil exports range from 500,000 b/d to 2 million b/d; an uncertainty which could cause prices to swing either way.