Oil is back under $100 a barrel

Oil prices have slipped below the $100 a barrel mark, amid a roughly 20% sell-0ff since early June.

Why it matters: Falling prices could disrupt the doom loop of rising inflation, rising interest rates, and rising expectations of further Fed hikes that have crushed the stock market this year.

Driving the news: Worries about weakening demand, which sent crude oil prices down 3.5% to $96.35 Thursday.

• A surprise increase in U.S. gasoline stockpiles — during peak driving season — suggests high gas prices are pushing consumers to cut back. Some think next week's GDP report could imply the U.S. is in a recession — at least by one technical definition. (A shrinking economy uses less oil.)
• Europe is slowing fast, amid an energy shock and inflation of its own. In response, the European Central Bank Thursday delivered a larger-than-expected rate hike, which will slow the economy even more, further cutting fuel demand. (The EU, if it were a single country, would be the world's second-largest consumer of crude.)
• China's economy — the actual second-largest crude consumer — is still in terrible shape.

The intrigue: Simultaneously, investment in crude production is picking up steam, says James West, head of oilfield service research at Evercore ISI.

• "We are starting to see some urgency and some acceleration in activity," he says.
• Mideast state-owned oil giants, international oil majors such as Exxon and independent Texas drillers unbeholden to Wall Street shareholders are all starting to pump more or ramp investment in order to do so, he says.

The impact: The combination of slipping demand and potentially increasing supply would support lower oil prices, though perhaps not drastically lower.

• "Nobody wants $100 oil," says West. "I think $80 is probably something people on both sides, producers and consumers, are very comfortable with."

The bottom line: Add investors to the list of those who'd love to bid adieu to the energy price spike, and to the overall inflation and Fed rate hikes that helped produce.

• With crude oil down 9% this month, stocks are enjoying their best month of the year — the S&P 500 is up over 5%.