TV stations nationwide make changes to their anchor teams on a regular basis, but it tends to happen less frequently in Pittsburgh, a competitive local TV market where stability reigns.

But changes at WTAE last week and on WPXI's morning news this week have viewers asking the same question: Why?

Why did WTAE shrink Sally Wiggin's air time? Why did WPXI dump Newlin Archinal? Why did KDKA fire Valerie Abati in July?

For every situation, there's a different answer. And sometimes there's not one concrete reason. TV stations will never tell, and the newscasters themselves often won't talk. But in most cases, the answer to "Why?" is a combination of factors, including:

Ratings: When ratings are down, changes are often made, particularly if the ratings correlate with the ...

Research: TV stations conduct focus groups to determine how viewers react to each piece of the on-air talent puzzle. Someone who is well-liked is said to have "high positives." An anchor who is polarizing may have high positives and high negatives.

Not all changes are research driven. Sometimes stations still rely on gut instinct, and management's favorites get promoted while others are demoted. That's probably part of what factored into recent WTAE changes that saw Andrew Stockey promoted to 5, 6 and 11 p.m. while Wiggin and Michelle Wright were reduced to one newscast per day (Wiggin at noon; Wright at 6 p.m.). Mike Clark is now on mornings and at noon. These changes also go hand-in-hand with ...

Cost containment: It's no secret that TV stations, like all media outlets (including newspapers), are suffering in an Internet-driven economy. Finding ways to cut costs is a top management priority.

Some viewers have suggested WPXI's Archinal, who anchored her final morning newscast Wednesday, was thrown overboard so the station could afford to bring back Julie Bologna, but WPXI news director Corrie Harding denied that's the case.

"This is a matter of improving a really strong morning show, and the budget considerations, whatever they might be and as confidential as those things are, did not enter into this," he said.

By moving a station's most veteran (re: more expensive) anchors into less-prominent time periods and/or by reducing their on-air time, when it's time for contract renegotiations, the station can make lowball offers based on these new assignments.

In larger markets nationwide, longtime star anchors have increasingly been replaced by younger, less expensive talent to contain costs. This is likely a factor in the changes at WTAE, particularly in light of comments made by WTAE alumnus Fred Young, senior vice president of news at Hearst-Argyle, which owns Channel 4.

"We won't be paying outrageous salaries for people to single-task," Young told TVNewsday.com in August. "We'll be looking for people who can multitask, who are willing to get out and, to use an old cliche, get their fingernails dirty and to report and to produce and to work the 24/7 schedules that our business requires."

Young also noted the era of high-priced anchors may be nearing its end.

"The ability of anchor talent to just leverage one station against another is going to end very soon because this is going to be all about what we can do within our communities and not what we can do to keep a small group of people happy," he said in the TVNewsday interview. "As news becomes more ubiquitous, I think that the team concept will be more important than the individual player."

And sometimes those individual players are ...

Not the right fit: KDKA's decision to jettison morning meteorologist Valerie Abati probably resulted from a mix of factors, including ratings. But seeing how she was replaced by veteran Dennis Bowman, it's clear one of the overriding issues was the homogeneity of KDKA's morning show mix. With Abati in the picture, the news team -- including Sonni Abatta, Keith Jones and Jim Lokay -- probably skewed too young for the older Pittsburgh market.

(Abati was hired last week at WLWT, the NBC affiliate in Cincinnati, to forecast at 6 and 11 p.m. Abati worked at the Fox affiliate in Cincinnati prior to her brief stint at KDKA.)

And in a relatively stable market like Pittsburgh, sometimes it's about setting the stage for ...

The next generation: So many primary anchors in Pittsburgh have such longevity that some changes may be about preparing for a new generation of lead anchors.

WPXI announced Wednesday that Jennifer Abney from WKRG in Mobile, Ala., will replace Archinal. Perhaps Channel 11 is beginning to stock the bench for a time when any of its evening anchors decide to call it quits.

For a long time it seemed like Wright would be the heir apparent to Wiggin at WTAE, but now that mantle has clearly passed to Wendy Bell, who continues to anchor at 5 and 11 p.m.

And at KDKA, morning anchors Jones and Abatta seem primed to step in should any of the station's evening anchors call it a career.

In her parting words on Wednesday morning's Channel 11 News, Archinal thanked viewers for their support during her nine-year tenure.

"The time has come for me to be able to redirect my personal ship into new waters," she said. "I am leaving Channel 11 today to start this new and exciting journey. Right now I can't say where I'm headed, but you will see me in a brand new way next year."

Archinal has refused to comment, so we're left to speculate. "Next year" may refer to sitting out a no-compete clause. And "brand new way" may mean something really different -- perhaps as the host of a weekly lifestyle show called "Newlin!" -- or maybe she's just going to another station.

Unless KDKA is planning to make big changes -- and I don't think it is -- there doesn't seem to be an open spot there. And WTAE just reconfigured its anchor teams, so it seems unlikely it would do it again so soon. We'll just have to wait and see.

KDKA's Patrice King Brown celebrated 30 years at the station Wednesday. Dave Crawley put together a feature that aired at 6 p.m. ... WTAE will air the Pittsburgh 250th birthday fireworks on a delayed basis tomorrow at 11:30 p.m., although it could air later depending on when college football ends. ... Tomorrow's "America's Most Wanted" (9 p.m., WPGH) includes a local case about a bouncer wanted for questioning in a shooting. ... Pittsburgh native and makeup effects wizard Greg Nicotero executive produces the Starz documentary "Fantastic Flesh: The Art of Makeup EFX" (10 p.m. Tuesday).

This week's Tuned In Podcast includes conversation about recent anchor changes at WTAE and WPXI and the season premieres of "Grey's Anatomy," "The Office" and "Desperate Housewives." Listen or subscribe at post-gazette.com/podcast.

Tuned In Journal includes discussion of the new season of "Survivor" and last night's vice presidential candidate's debate. Read it at post-gazette.com/tv.