FAST cars whizz around,malls are full of expensive luxuries and cranes dominate the skyline.But scratch the shimmering surface of the Gulf and you soon find countries hurting from the low oil price,currently around $40 a barrel.Growth is slowing and unemployment is rising.Policy makers even dare utter a three-letter“t” word until recently taboo：tax. Oil is central to the six Gulf Co-operation Council（GCC）states,which have used the windfall of the past few years to spend lavishly.Unlike many oil exporters,such as Nigeria and Venezuela,they have high foreign exchange reserves and low debts to cover short-term gaps.But public spending is generous and the private sector is heavily reliant on oil to boot.To be sustainable in an era of lower prices.the rulers must change the structure of their economies. The IMF reckons the lower oil price knocked $340 billion off Arab oil-exporting states’ government revenues in 2015.This year is looking worse.Moody’s,a ratings agency,this month downgraded Bahrain and Oman and put on watch the other four GCC states： Saudi Arabia,Kuwait,the United Arab Emirates （UAE） and Qatar.“It’s the end of an era for the Gulf,”says Razan Nasser of HSBC in Dubai.“And we’re only just starting to see the effects.” Oil receipts typically account for more than 80% of GCC government revenues,rising to over90% of Saudi Arabia’s budget before the crisis.Dubai,one of the emirates making up the UAE,is an exception,with oil accounting for only 5% of revenues.That is because it has successfully diversified tourism and services account for most of its government revenues. Governments are reacting to the squeeze on their incomes with a mixture of strategies,drawing down reserves and taking on debt on the one hand,and imposing spending cuts on the other.Last year they made tweaks,such as curbing benefits for public servants.This year will be tougher.Oman has told all state-owned enterprises to remove perks such as cars.Qatari companies including Al Jazeera and the Qatar Foundation,a cultural organization,have laid off employees.With such tweaks, Kuwait,the UAE and Qatar,which have small populations and high foreign exchange reserves,can get by for a decade.