[Jason.]

If you think about it:

BB14 was like the BB7 of C5, in that production started to up the ante by having more twists, but both were successful, so they got away with it.

Then BB15 was like CBB5, in that it tried to replicate the success of the former series but it backfired as the producer's decisions ended up having a negative effect on the series (putting Jade back in led to the race row and giving Helen a pass to the final made the series more negative and draining)

BB16 was like BB8 in that it started of well, but the ratings were lower than usual, so they introduced unnecessary twists as a way to increase ratings, but that ended up hindering more than it helped and the ratings got worse.

BB17 was like BB9 in that it was a step in the right direction after a slight decline.

BB18 was like BB10 in that the ratings fell even further and the show was beginning to feel stale. This is also when speculation of the show being axed began, just like it did at the time.