Beckett and Castle will be back on the case next season. Their TV show has been renewed for a fifth year by ABC.

Though the demo ratings for Castle have been on the decline this season, ABC has given the go-ahead for another round of episodes. Airing on Monday nights, Castle’s fourth season averaged a 2.3 rating in the coveted 18-49 demographic with 10.71 million viewers.

Year-to-year, the demo is down by 15%. Interestingly, the total viewership is almost exactly the same. That would seem to indicate that the show has picked up older viewers (Dancing with the Stars has also been declining but skews older) but lost some younger ones — potentially to NBC’s Smash.

On our ABC Ratings Report Card, which measures the relative demo performance of shows on the network, Castle has a “C+” grade. It’s #12 on the demo list of scripted shows but ranks #2 in terms of total viewers.

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Though the ratings were enough to put the show “on the bubble,” it realistically wasn’t in any danger of being cancelled. ABC hasn’t had much luck finding successful new hour dramas this season.

More importantly, Castle presently has 81 episodes and that’s not really enough for a full syndication package. Last June, TNT picked up the cable rights to for Castle so ABC Studios has additional financial incentive to keep the show around.

ABC announces their 2012-13 schedule next week so we’ll know by then if Castle will stay on Monday nights or pop up on another evening instead. Either way, you can expect it to return next fall.

What do you think? Are you glad that Castle has been renewed? Are you still enjoying the show or do you think the quality has started to drop?

Image courtesy ABC.