Seniority and Pay Parity
It's important to look at the seniority argument from a real-world perspective. Seniority is rarely, if ever, the single determining factor in deciding how much to pay an employee. Many other things factor into the equation. What qualifications did the employee bring with them to the company? How much does the employee bring to the company monetarily? Is the employee well-liked by their colleagues and customers? These are just a few other contributing factors in salary determination.
There's also the question of paying your "dues" -- Cote had been on the show for 8 years and had helped pull in ever increasing ratings. Her screen time increased over her 8 years on the show, why shouldn't her pay have increased accordingly? Especially when you factor in that her episode "Shiva" (January 15, 2013) pulled in the most viewers in the NCIS' 10 year history. 25.36 million viewers in L+3, based on CBS' own press release. At what point do you become a proven commodity and valuable to your employer or are you always expendable?
One Year Contract vs Multi-year Deal
If there's one thing that NBC's Friends showed the television industry, it's that having your cast on the same contract schedule can be a nightmare if the cast decides to collectively bargain. In the case of Friends, NBC had little leverage with the entire cast giving them only two options: either pay each member a whopping one million dollars per episode or let the case walk and have their biggest revenue source disappear.
The NCIS case is different, though, for two reasons. The first being that sitcoms and dramas are two completely different beasts and the second being that, while NCIS may be the #1 show on television, it is not CBS' largest source of revenue.
Nevertheless, allowing Cote to sign a one year contract, rather than a multi-year deal, meant that CBS would have been taking the risk that the cast would try to collectively bargain for higher salaries and bigger bonuses, an opportunity that Cote had never had before because her contract was on a different cycle than everyone except Mark Harmon's. The way networks view it, having fewer actors on the same contract schedule means more power and leverage they have during negotiations. According to a Deadline article by Nellie Andreeva, CBS has previous experience with its NCIS stars bargaining together as was done during the 2011 contract cycle, during which CBS low-balled Pauley Perrette, Michael Weatherly, Sean Murray and David McCallum.
Opportunity Cost
However, this issue is not one-dimensional. Yes, conceding to a one-year deal means the possibility of having to deal with collective bargaining, but there's also another business aspect to be taken into consideration in these circumstances: opportunity cost. For anyone who did not take economics or business in college, opportunity cost is what one sacrifices by selecting one course of action over another alternative. Basically, "what you lose when you choose."
So what does a CBS stand to lose by not paying females equally? What are the opportunity costs of choosing not to grant Cote the salary and contract terms she was asking for? Opportunity costs aren't always financial. For a television network, they can extend to employee morale, loss of employee productivity, cost of casting for a new role, potential loss of viewership and ad revenue, fan outcry and loss of consumer (viewer) brand loyalty and strain on PR resources.
By all accounts, the NCIS cast and crew is "like a family." And losing a member of one's family is hard, especially when it happens unexpectedly. But what effect does that loss, and the conditions surrounding it, have on the family members that are left? On a TV set this can mean diminished employee morale. Yes these are professionals, but "one man down" undoubtedly affects the atmosphere on set. Maybe the cast and crew become distracted by the abrupt change or they begin to wonder if perhaps they themselves are not as valuable to the network as they had once thought they were. Perhaps cast members even start to consider making a change themselves.
Last-minute casting changes also affect employee productivity. Not just for cast and crew, but for producers and writing staff as well. On NCIS, this meant last minute script re-writes just says before shooting and having to re-map an entire season's worth of story lines in a very short amount of time. These quick-changes can translated to even longer working hours for cast and crew as they try to wade through the "what now" of it all. So while the show must go on, it may likely do so at the expense of quality.
So the show has lost a major character. What happens next? Casting. An expensive and time-consuming task for which the network and studio will not see a dollar for dollar return on investment. The process involves a lot of decision makers. Casting directors, producers and studio and network executives all must agree on who is to be cast. In an established show, they run the risk that the person cast may not be a good long-term fit for an already-established cast. Or everyone, cast included, thinks the new actor is a good fit, but the audience doesn't like the new addition. Maybe the audience gives the addition a chance or maybe they stop watching.
Some may look at the Nielsen ratings for season 11 and point out that NCIS still has 19 million viewers on average -- so why the need for concerns over viewership numbers? Perhaps that might be true, but it's worth noting that a competitive landscape can change in the blink of an eye.