While the broadcast networks count the days until the end of summer, cable television networks may wish the season would never end. As another summer comes and goes, cable TV has once again inched further ahead of broadcast in the ratings.

Cable TV’s average rating in the 18-49 demographic is up 1.3 percent over last summer, to a 16.1, according to a new Magna Global analysis of Nielsen Media Research ratings, while broadcast has taken another tumble, down 14.3 percent, to a 7.2.

Further, ad-supported cable's share of the 18-49 audience in primetime continues to rise, up 3 percent to 52.4 percent from 50.8 percent last summer, while broadcast's sinks ever further, to 24.3 percent from 27.3 percent a year ago, according to Turner Broadcasting. That's down 10.9 percent. 

And once again, credit goes to the flush of hit original series on cable.

"There are more scripted series than ever,” says Brian Hughes, research manager at Magna. “People have come to expect the scenario in the summer where if they want to watch good scripted programs they go to cable because the networks generally don’t do too much scripted programs in the summer.”

Among cable's hot summer originals are Lifetime’s “Army Wives,” its highest-rated show ever, TBS's “House of Payne” and “The Bill Engvall Show,” and USA’s “Starter Wife.”

“Original shows do a lot of things for a network,” explains Tim Brooks, executive vice president of research at Lifetime. “It attracts advertising dollars. You can get premiums for [originals]. It attracts viewers to the network, which can be used for promos for other programs. That’s why so many networks are getting into this area.”

But it's not just the big cable networks that are doing well with originals this summer. The smaller cable networks are moving aggressively into original series.

AMC two weeks ago premiered its first original scripted series, “Mad Men,” from “Sopranos” writer Matthew Weiner, and saw its rating surge 75 percent above its Thursday average. The network has other originals coming, including the drama “Breaking Bad,” which will premiere in January.

“Original programming is an opportunity to be distinct,” says Charlie Collier, general manager and executive vice president of AMC. “What a series allows you to do, when you have movies at your core, is have people come back at the same time, week after week, for something that is brand-reinforcing.”

The cable networks are also doing well with original reality shows.

The History Channel’s “Ice Road Truckers,” for instance, ranks No. 11 so far this summer among original cable programs, according to Magna. Ranking close behind are shows like “Next Food Network Star” and VH1’s “Charm School,” which finished its run earlier this month.

And Discovery Channel generated its best-ever premiere rating on Sunday for an original program, which aired during its annual “Shark Week.” “Ocean of Fear: The Worst Shark Attack Ever” had an audience of 3.9 million people.