The decline in the price of oil is like a shot in the arm for the global economy.

If this year Christmas seems merrier, and Hanukah happier, the unexpected gift from Saudi Arabia last month in not cutting production amid an oil glut may have had something to do with it.

And if that gift keeps on giving—gas prices have now declined 88 straight days, the longest streak on record, according to the The Wall Street Journal—U.S. shale producers can also be thanked. The Journal reports that shale oil producers are facing a classic prisoners’ dilemma, each hurt by the oil glut but each waiting for its rivals to make the move.

If one’s competitors cut production, the firms still producing benefit from the resulting higher prices and diminished competition. They also avoid big risks that come with turning off the tap: “Cutting back on oil production would be risky for companies, which could lose market share, not to mention the cash they need to pay off debt and drill new wells.”

While oil producers are hurting, the decline in the price of oil to about half its $110 a barrel peak over the past five years, is like a shot in the arm for the global economy.

Mark Luschini, chief investment strategist at Janney Montgomery Scott, told ThinkAdvisor in an interview that the oil price decline should result in expansion of global GDP.

“The IMF estimates that every 10% decline in oil prices equals a boost of 0.2-0.4% [in] global GDP over two years,” says Luschini, whose investment firm oversees $67 billion in assets. “Where oil rests today suggests [a boost of] 1-2% roughly or 0.5-1.0% next year. In addition, the five largest oil importers—the U.S., Euro area, China, Japan and India—will benefit from the cheaper price and collectively their economies represent 2/3 of world GDP.”

That GDP expansion derives from the net increase in consumer demand and takes into account the “negative” disinflationary impact the oil price plunge has on consumer spending.

“The [oil price] decline [will not] arrest disinflation as oil’s fall will actually contribute to it,” Luschini continues. “But core CPI should get a bump from increased consumer and business activity.”

Consumers’ ability to spend their income on Christmas gifts rather than gas at the pump has provided a nice holiday bonus for U.S. (and global) consumers.

Jason Pride and Casey Clark of Glenmede, a  family-office-type firm and trust companywith $27 billion in assets under management, calculate that the reduced price of gas could amount to a 2% raise for the average consumer and significantly more for lower-income Americans for whom energy expenditures represent a higher proportion of spending.

Those figures, in a December market insight, are based on data prior to the oil price decline’s most recent plunge, and so may understate the benefit to consumers.

The Glenmede research team notes that the net impact of the fall in energy costs will have a disparate impact across the globe. Naturally, oil exporters like Saudi Arabia and Iran are hurt most by the price plunge, while an oil-starved nation such as Argentina will benefit most.

But while the U.S. will benefit overall—Treasury Secretary Jack Lew compared today’s prices to “a tax cut to the economy”—U.S. oil producers, now “transformed” to global titan status thanks to the shale oil boom, will be severely affected.

“A meaningful portion of our post-recession recovery is attributable to the growth of the energy sector, as the shale boom has directly created a more prosperous and diversified U.S. economy,” Pride and Clark write.

They cite estimates from The Economist newspaper that with oil under $65 a barrel (it’s currently hovering at nearer $55 a barrel), the U.S. could see industry investment fall by 20% and production growth slow to 10% a year.

Because the U.S. both gains and loses in different ways as a result of the oil price plunge, the Glenmede team expects a “muted impact” domestically, but a lift for oil-dependent Europe and Asia, leading to “a more balanced global economy and marketplace.”

The price decline’s impact on monetary policy is also noted. By further suppressing inflation, lower oil prices “provide an excuse for the Federal Reserve to delay or slow its rate-hike plans.”

While the stock market as a whole seems to be getting a lift, the energy sector has been battered. “The XLE energy ETF is down 25%, and few, if any, equities in the sector have been spared,” write Pride and Clark.

While Pride, Glenmede’s director of investment strategy, is monitoring markets for “opportunistic entry points,” he and Clark are counseling patience for now.

“Sector-specific declines do not disappear overnight, as investors require time to adjust their expectations for the newer reality,” they write.