An average of 50,000 people spent each night in a New York homeless shelter in January — about 22 percent more than last year — though a Wednesday report from the Bloomberg administration says the number of people with nowhere to go has declined by 28 percent since 2005. The city’s survey put the population of “unsheltered” homeless in January at 3,180, and estimated that 1,841 of them were sleeping on the subways that freezing month — a 13-percent increase from the previous year, and a 118-percent increase from 2005, which is when officials began keeping track. Mary Brosnahan, the head of Coalition for the Homeless, called the tally “deeply flawed” and said its claim “that street homelessness is down completely lacking in credibility.” Department of Homeless Services commissioner Seth Diamond called that critique “outrageous and irresponsible” — kind of like his boss’s claim that no one is sleeping outside at all.