THE boom that adorned Gulf Arab monarchies with glittering towers, swelled their sovereign funds and kept unrest largely at bay may be over after oil prices dropped by almost 50 per cent in the last six months.

The sheikhdoms have used the oil wealth to remake their region. Landmarks include man-made islands on reclaimed land, as well as financial centres, airports and ports that turned the Arabian desert into a banking and travel hub. The money was also deployed to ward off social unrest that spread through the Middle East during the Arab Spring.

"The region has had 10 years of abundance," said Simon Williams, HSBC Holdings Plc's chief economist for central and eastern Europe, the Middle East and North Africa.

"But that decade of plenty is done. The drop in oil prices will hurt performance in the near term, even if the Gulf's buffers are powerful enough to ensure there's no crisis."

Brent crude, which has averaged US$102 (RM356) a barrel since the end of 2009, plunged to about US$60 by the end of last week.

The slump accelerated after the Organisation of Petroleum Exporting Countries, whose top producer is Saudi Arabia, decided in November to keep output unchanged.

At US$65 a barrel, the six nations of the Gulf Cooperation Council, which hold about a third of the world's crude reserves, would run a combined budget deficit of about six per cent of gross domestic product, according to Arqaam Capital, a Dubai-based investment bank.

Cheaper oil "will force a reassessment of the ambitious infrastructure investment programme" in the region, Qatar National Bank said in a report.

One exception is likely to be Qatar, which is spending on infrastructure to host the 2022 soccer World Cup final, QNB said.

The oil-price drop has already prompted economists to cut next year's growth estimates for Saudi Arabia, the United Arab Emirates and Kuwait.

The GCC spending spree hasn't resolved problems such as high youth unemployment, especially in Saudi Arabia, where the rate was close to 30 per cent in 2012, according to the International Monetary Fund.

"Lower oil prices will be a real test," said Crispin Hawes, managing director of research firm Teneo Intelligence in London.

"If there was a problem in the past, they threw sacks of cash at it."

That cash also financed a global spending spree. Qatar, the richest country in the world on a per-capita basis, has holdings in Harrods department store in London and in banks such as Barclays Plc.

Abu Dhabi's national carrier Etihad Airways made a string of purchases, including a multi-billion-dollar investment in Alitalia SpA. Bloomberg