UPDATED: Every year, the estimated number of U.S. households owning TV sets goes up. Until now.

According to Nielsen’s annual “Television Audience” report that was released this week, the number of households with a TV set will decline. The rising trend of TV ownership has been leveling off in recent years, and now the number has dropped from 115.9 million homes in 2011 to an estimated 114.7 million in 2012. As TV Barn pointed out, that’s a 1 percent decline despite the number of households rising.

TV ownership among the key adult 18-49 demo also declined, and even steeper (down 2.7 percent — a downtrend that started to a slight degree in 2010 and then accelerated this year). Plus, the percentage of homes without a TV is at the highest level since 1975 (3 percent, up from 1 percent the previous year).

Why is this happening? There’s a few factors that could be at play, including more people watching TV shows online and the distressed economy.

Meanwhile the rich get richer: Homes with three or more TV sets will climb a notch to 56 percent.

Here’s the chart from Nielsen:

UPDATE: A Nielsen rep, after seeing media stories reacting to their report and chart, emailed to clarify that TV ownership has actually declined once before: In 1992, “after Nielsen adjusted for the 1990 Census, and subsequently underwent a period of significant growth.”