The Bengalis make up 98% of the total population of Bangladesh, making it one of the most ethnically homogeneous states in the world. The large Muslim population of Bangladesh makes it the third-largest Muslim-majority country. The constitution declares Bangladesh a secular state, while establishing Islam as a state religion. As a middle power in world politics, Bangladesh is a unitary parliamentary democracy and constitutional republic following the Westminster system of governance. The country is divided into eight administrative divisions and sixty-four districts. Although the country continues to face the challenges of the Rohingya refugee crisis, corruption, and the adverse effects of climate change, Bangladesh is one of the emerging and growth-leading economies of the world, and is also one of the Next Eleven countries, having Asia's fastest real GDP growth rate. The Bangladeshi economy is the 39th-largest in the world by nominal GDP, and the 29th-largest by PPP.