Bunting is not as hellishly bad as it's been cracked up to be lately. What I've often seen are run expectancy charts that calculate the average runs in a runner/out matrix., and then used as such: "That bunt decreased the expected runs that inning from 1.58 to 1.01! Fire [insert manager's name here]!"
What I dislike about this is that A) win expectancy should be used instead of run expectancy, and B) it takes a macro view of the situation. It uses all the data available, so it's essentially an average hitter against an average pitcher, playing behind an average defense, in a non-specific inning, year and score (in addition to many other "average" factors). That never happens in a real game.
If [the defensive manager] suspects a bunt, they play up and if they suspect a hit away, they play back, and if they are not sure, they play somewhere in between, exactly what they should be doing. On offense though, managers are way too predictable. Their mistake generally is not that they bunt too much or too little (although many managers do). It is that they don't understand the concept that they should be mixing up their bunts and non-bunts on a random basis. This is a difficult concept for anyone to understand, much less a baseball manager. So, instead, they generally have it in their head that a bunt or non-bunt is 100% warranted in any given situation, and in most cases, the opposing manager on defense knows the same thing...
They have it in their head that they are going to bunt whether the defense is playing all the way up or not. And, as I said, in most cases, this is wrong. If the defense is going to play all the way up, anticipating the bunt nearly 100% of the time, the offense must make them pay for that by not bunting a high percentage of the time at least until the defense starts to move back - and then the "jockeying" can continue. And finally, some managers do not adjust their strategies as the count changes. Clearly if the count is in the batter's favor, he should be less likely to bunt and the defense should move back, and if the count is in the pitcher's favor, but not with 2 strikes, the batter should be more likely to bunt and the defense should move up.
The following is partly a summary of the ideas in the article and partly some of my own thoughts on the factors that play a part in the decision to bunt or not.
Year: The "run environment" can have an affect. The lower it is, the more important bunting is (the same with stolen bases). When fewer runs are being scored (think the 1960s), bunting makes more sense. As we see a "return to normalcy" in runs scored this year and last (as opposed to the 1995-2009 run environment, which was among the highest in history), bunting may creep back into the game. 4.16 runs/game is the current average, which is the lowest since 1992.
Inning/Score: Bunting should be used more often late in a close game, when one run has more impact on the win expectancy than early on. Down by several runs, bunting is usually not a good idea.
Count: Bunting with two strikes is obviously not a good idea, but when it starts favoring the hitter (2-0, 3-1), the odds of a hit or walk increase, so swing away.
Defense: This is a big one. The offense gets an advantage by seeing where the defense is before the pitch is ever thrown. Is the infield playing back or in? Is the shift on? Are the corner infielders any good (is it Don Mattingly or Jason Giambi at first - Brooks Robinson or Ty Wigginton at third)? What about the pitcher and catcher?
Batter: Another big one. The better a hitter is, the less he should bunt. The faster he is, the more he should bunt. Is he actually a good bunter? Is he a GDP candidate? Is he hot or cold? How's his history against the pitcher?
Pitcher: How good is the pitcher? Is he tiring? Does he have the platoon advantage? A strikeout/groundball pitcher is a better candidate to bunt on. A flyball pitcher obviously is not, because the chances of a bunt pop-up and home run increase.
Game Theory: Sometimes even power hitters should bunt, not only because they can buy an easy single, but because it will keep the defense more honest in the future. Oft-times the situation in when you'd least expect a bunt results in the highest chances of a successful bunt (purely because the defense is not expecting it). Remember, this is not happening in a vacuum. If a manager bunts often, his opponents will get wise to him and eventually bring the infield in. When this happens, he should then let the hitters swing away. It's all about adjusting and re-adjusting for success in the long run. Of course, in the playoffs, managers should go with whatever gives them a greater chance to win that one game, long run be damned.
Miscellaneous: Who is due up after the bunter/hitter? Is the ballpark pitcher or hitter friendly? Is the bullpen rested? (If Mariano is unavailable, maybe it's best to play for the big inning, while if he is, the converse might be best.)
The (very) basic order of who should bunt and how often:
Almost never - slow power hitters (Dunn, Ortiz)
Rarely - fast power hitters (A-Rod, Grandy)
50/50 - fast mediocre hitters (GGBG, Jeter)
Often - pitchers (at least with men on base)
The above would also depend on the defensive alignment.
Bunts are less frequent in the modern era than in any other previous era. The issue is partially that hitters nowadays are just so bad at bunting. Anecdotal evidence suggests they just don't practice it as much as they used to, so managers use it less. (Or do they become bad bunters because they're not asked to do it as much? Chicken or the egg...) Another problem is the sac bunt. Stats show that bunt attempts for hits are more successful at both reaching base and, therefore, producing runs than bunting with the sole purpose of making an out.
Anyway, hopefully I've given lots of food for thought.
Look for the preview for tonight's game at 7 p.m.