WASHINGTON — The number of chronically homeless people living in the nation’s streets and shelters has dropped by about 30 percent — to 123,833 from 175,914 — between 2005 and 2007, Bush administration officials said on Tuesday.

Housing officials say the statistics, which the Department of Housing and Urban Development collects each year from more than 3,800 cities and counties, may reflect better data collection and reporting and some variation in the number of communities reporting on an annual basis. But the officials attribute much of the decline to the “housing first” strategy that has been promoted by the Bush administration and Congress and increasingly adopted across the country.

In that approach, local officials place chronically homeless people into permanent shelter — apartments, halfway houses or rooms — and then focus on treating addiction and mental and health problems. HUD defines chronically homeless people as disabled individuals who have been continuously homeless for more than a year or have experienced at least four episodes of homelessness in the past three years.