In rec.radio.shortwave on 18 Mar 2004 17:42:42 GMT,
(Michael Black) wrote:

Using WWVB, at least for consumers, is a relatively recent thing, like
in the past decade. I'm not sure why they moved from WWV to WWVB, but
clearly there is more penetration of WWWV-based clocks than WWV-based
clocks. I bought one for $20 Canadian in February, and that sure beats
any WWV-based clock in terms of cost.

The avalance of WWVB-enabled devices (such as the $30.00 wris****ch I'm
wearing) began in earnest after the signal was beefed up (new[er] transmitters,
antenna improvements, etc) in 1997 - 1999. See

http://www.boulder.nist.gov/timefreq/stations/wwvbhistory.htm

mdr