There’s one sector of the entertainment industry that has not been roiled by the Internet, the economy or ever-changing consumer tastes. Say hello to Hollywood’s most stable business: Soft-core pornography.

The oft-mocked genre, which has given the world such memorable fare as “Witches of Breastwick” and “Tarzeena: Jiggle in the Jungle,” is more visible — and valuable — than ever, even at a time when hard-core adult entertainment is easily accessible on every media device. Premium-cable TV networks such as HBO, Showtime and Cinemax — the channel nicknamed “Skin-emax” for its preponderance of sexy programming — continue to fill their late-night schedules with low-budget, nudity-filled films, and the adoption of video-on-demand and pay-per-view services has given soft-core content wider play. Several of the premium channels offer prominently displayed inventories of erotic entertainment via VOD, where there’s no shortage of choices in the “After Hours” or “Midnight Movies” sections.

Soft-core porn “just keeps going, like a cockroach — you can’t kill it,” says Marc Greenberg, the 63-year-old founder of MRG Entertainment, the Santa Monica company that’s one of the top producers of so-called “soft erotics,” the industry term for toned-down pornography. MRG supplies between seven and 15 films a year to Showtime and a handful of movies to Cinemax, for whom it also produces “Co-Ed Confidential,” a 13-episode, college-themed sex series that’s now in its fourth season. “You’re more likely to get your wife to watch my show — it’s not so in-your-face,” says Greenberg.

At the same time, premium channels have been upping the skin factor on their higher-profile, higher-brow series. Shows such as HBO’s “True Blood,” which debuts its third season next month, and Showtime’s “The Tudors” and “Diary of a Call Girl” all showcase fairly graphic sex scenes that are often as explicit as what you would see in an R-rated movie in theaters. In one memorable scene from the first season of Showtime’s Emmy-nominated " Californication,” which stars David Duchovny as a lothario novelist living in Venice, his character engages in a ménage à trois with his agent, played by Evan Handler, and a beautiful 20-something woman. The romp climaxes just as their ex-wives walk in the door.

It’s no secret, of course, that sex sells, and cheesy erotic content has been a constant on cable TV since its early days, long before premium networks expanded into multichannel behemoths. Showtime, for example, now offers eight channels on its “multiplex” package, including Showtime Women, a female-targeted channel that does not show soft porn.

All of the premium channels will air films that are rated X by the Motion Picture Assn. of America, but they also adhere to certain self-imposed guidelines when it comes to sexy material. In general, cable channels won’t show full male frontal nudity or extended close-up shots of female private parts. “Our producers know where the lines are,” says Susan Ennis, executive vice-president of program planning for HBO Networks, which owns Cinemax.

Erotic entertainment “is a staple of [Cinemax’s] brand, it’s in our DNA, we’re not running away from it,” Ennis says..

Cinemax’s volume of soft porn has been steady for the last five years, and it continues to roll out one new sex-themed series per quarter, with the most recent being the second season of “Zane’s Sex Chronicles,” based on a bestselling series of erotic short stories written by Zane, the pen name of a female African American author from the Washington, D.C., area.

Across all platforms, the series, which follows the romantic adventures of a group of professional women, attracts about 1.4 million viewers per episode, according to the network, which has nearly 12 million subscribers. “I don’t think that sexuality should be separated from the rest of life — it can be fun, it can be painful, it can be kinky and it can be entertaining in a tasteful way,” says the 43-year-old author known as Zane, who writes all the scripts for the series and is its executive producer. Adds Ennis: “We know our viewers embrace this kind of content.”

That content is particularly conspicuous now on VOD, which has unshackled soft-core from the boundaries of late-night. On Cinemax, erotic films and shows — what it calls “After Dark” content — make up just 8% of the channel’s over-the-air schedule. But when it comes to VOD, nearly 20% of Cinemax’s inventory is devoted to erotic entertainment, and 15% of the channel’s overall on-demand orders are for “After Dark” programs.

Ironically, the proliferation of hard-core porn in recent years seems to have made the softer stuff more appealing — or at least more palatable — to a wider audience, particularly among women, according to industry observers. While women who are now in their 20s and 30s have grown up in an era when adult entertainment has become increasingly mainstream and sex tapes helped launch the careers of celebrities such as Kim Kardashian and Paris Hilton, many of them are still uncomfortable watching all-out porn, even if it’s in the company of a partner.

In contrast to hard-core pornography, which depicts full male nudity and actual sex, soft-core sex is more simulated than real, and the films usually attempt to have coherent storylines and dialogue. Many of the soft-core TV series also center around a female character, such as the madam in “Beverly Hills Bordello,” a longtime cable-TV staple, or the pair of sisters — one a recent college graduate, the other an erotic model — who are the leads in “Life on Top,” a Cinemax series that debuted last year. But while soft-core content may be less graphic than a Jenna Jameson film, it does not aspire to high art.

“There’s nothing creative about this — you’re going to see sex in the first minute and you’re going to see sex every seven or eight minutes after that,” says Greenberg.