An Afghan boy waits for customers to buy cigarettes, sweets and mobile phone credit cards during a snowstorm in Kabul, Afghanistan, Monday, Feb. 4, 2013. Kabul has been experiencing below freezing weather and snow for several days. AP Photo/Musadeq Sadeq Afghan boys warm their hands over a brick factory fire during a cold day in the outskirt of Jalalabad east of Kabul, Afghanistan, Monday, Feb. 04, 2013. AP Photo/Rahmat Gul KABUL, Afghanistan (AP) - The United Nations says the cost of corruption rose sharply last year, and half of all Afghans bribed public officials for services. The U.N. says that while the number of people paying bribes actually declined by 9 percent from 2009, the amount of bribe money rose by 40 percent, to $3.9 billion. It says education has become one of the most vulnerable sectors, and the number of Afghans bribing a teacher jumped from 16 percent in 2009 to 51 percent in 2012. The findings are based on a survey of 6,700 Afghans released on Thursday by the U.N. Office on Drugs and Crime and the Afghan anti-corruption unit. The international community has long expressed concern about endemic corruption in Afghanistan because it reduces confidence in the Western-backed government.