Well, the first caveat is nobody makes these decisions based on 6+ numbers...
At the end of the day, revenue is all that matters. If I change the programming to raise the share but my billing remains flat, then there was no real reason to change the programming... unless the new programming costs substantially less and improves profitability. But if you can grow the audience in demos that you can sell, the ratings boost should increase your billing.
The other part of the equation is cluster strategy. If one station is eating away at the core of another, then nobody wins. Some stations will set up a "wall of men" or a "wall of women" with each aiming for a different age group. Others will aim for the same age group but focus one station on men and the other women. It all depends upon the market. The clusters that do the best are ones where everyone fights to be number one, but the formats are arranged where they can win by hurting competing groups and not themselves.