CBC Television:

Until 1998, the network carried a variety of American programs in addition to its core Canadian programming, directly competing with private Canadian broadcasters such as CTV and Global. Since then, it has restricted itself to Canadian programs, a handful of British programs, and a few American movies and off-network repeats. Since this change, the CBC has sometimes struggled to maintain ratings comparable to those it achieved before 1995, although it has seen somewhat of a ratings resurgence in recent years. In the 2007-08 season, hit series such as Little Mosque on the Prairie and The Border helped the network achieve its strongest ratings performance in over half a decade.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". For how long has the CBC maintained its lead over other broadcast networks?
unanswerable