Here’s a Nielsen shocker: The number of homes in the U.S. with television sets is declining for the first time in 20 years.

Nielsen’s preliminary universe estimate for 2012 counts 114.7 million television households in the U.S., down from 115.9 million in 2011. That means the total penetration of TV in the U.S. has dipped to 96.7% of the population from 98.9%. Nielsen’s latest household and demo estimates reflect the latest population data gathered from the 2010 Census.

Nielsen cites the shaky economy, the transition to digital broadcasting and the growing number of viewers opting for Internet-based TV services as factors for the decline in TV households. According to the report, the cord-cutting factor is particularly strong among what Nielsen described as “a small subset of younger, urban consumers (who) are going without paid TV subscriptions.” The report noted that the last drop in TV set ownership was in 1992, following a recession, and that it was followed by a period of ‘significant growth” in TV households.

“Some consumers are clearly being driven by the economy to make choices on the media devices they purchase. Others are expanding their equipment to add more audio/video devices to their home. Still others may be deferring a TV purchase or replacing their TV with a computer,” said Pat McDonough, senior veep of insights and analysis for Nielsen.