The United Nations is celebrating an Indian government program officials say can be a model for other low-income and developing countries at a summit this week in New Delhi. But in Taimoor Nagar, a slum just outside one of the city's poshest neighborhoods, hundreds of people rely on a single public toilet, underscoring the challenges that remain for India's urban poor. The numbers in the government's ambitious Swachh Bharat, or Clean India, program are staggering. India's population of 1.3 billion accounted for 60 percent of the world's open defecation in 2014, when Prime Minister Narendra Modi came to power, but that dropped to 20 percent by 2018. The summit — with a keynote address by UN Secretary-General Antonio Guterres on Tuesday — overshadows the struggles with open defecation that remain in the heart of India's capital. The $20 billion program concludes in 2019, timed to coincide with the 150th anniversary of Mahatma Gandhi's birth. The freedom fighter wrote in 1925 that many diseases in India were caused by a "bad habit of disposing of excreta anywhere and everywhere."