after calling for his country to have a 60 percent stake in the Chad-Cameroon oil output after receiving "crumbs" from foreign companies running the industry. He said Chevron and Petronas were refusing to pay taxes totalling $486.2 million. Chad passed a World Bank-backed oil revenues law that required most of its oil revenue to be allocated to health, education, and infrastructure projects. The World Bank had previously frozen an oil revenue account in a dispute over how Chad spent its oil profits, with Déby accused of using the funds to consolidate his power. Déby rejected those claims, arguing that the country does not receive nearly enough royalties to make meaningful change in the fight against poverty. 2010s On 25 April 2011, Déby was re-elected for a fourth term with 88.7% of the vote and reappointed Emmanuel Nadingar as Prime Minister. Because of Chad's strategic position in West Africa, Déby sent troops or played a key mediating role in tackling multiple regional crises, such as Darfur, the Central African Republic (CAR), Mali, as well as the fight against Boko Haram. With the security situation in the Central African Republic deteriorating, Déby decided in 2012 to deploy 400 troops to fight the CAR rebels. In January 2013, Chad also sent 2000 troops to fight Islamist groups in Mali, as part of France's Operation Serval. Chad's recent history, under Déby's leadership, has been characterized as having been rife with endemic corruption and a deeply entrenched patronage system that permeated society, according to Transparency International. The recent exploitation of oil has fueled corruption, as revenues have been misused by the government to strengthen its armed forces and reward its cronies, which contributes to the undermining of the country's governance system. In 2006, Chad was placed at the top of the list of the world's most corrupt nations by Forbes magazine, In 2012, Déby launched a nationwide anticorruption campaign called Operation Cobra, which reportedly recovered some $50 million in embezzled funds. Nongovernmental organizations say, however, that Déby has used such initiatives to punish rivals and reward cronies. As of 2016, Transparency International ranked Chad 147 out of 168 nations on its corruption index. Faced with a growing threat from Boko Haram, Déby increased Chad's participation in the Multinational Joint Task Force (MNJTF), a combined multinational formation comprising units from Niger, Nigeria, Benin, and Cameroon. In August 2015, Déby claimed in an interview that the MNJTF