Eras Rates

The "Rates" tab enables you to create and modify some important information about the era.

There are three groups of rates on this page. The first group determines pitcher durability, the second determines error rates, and the third governs the pitch-by-pitch system. Let's consider each group in turn.

Average pitches

The values for average pitches per start and per relief appearance determine how quickly your pitchers will get tired.

Keep in mind that there are many reasons other than fatigue for a pitcher to be removed from a game -- ineffectiveness, the need for a pinch hitter, a double-switch, injury -- so the average number of pitches thrown is usually lower than the number of pitches he can throw before getting tired in any particular game. This is, of course, assuming the pitcher doesn't enter the game having already thrown a bunch of pitches in the last couple of days.

For example, if the average number of pitches thrown per start is 95, a pitcher with an average durability rating can probably throw at least 110 pitches before tiring if he enters the game at full strength. And a pitcher with an Excellent durability rating can probably throw more than 130 pitches before beginning to weaken.

See Pitching Ratings for a table showing how the average number of batters faced has changed over the past 100 years. You can use this table as a guide when choosing the average pitch values for your eras. You'll need to multiply these batter faced numbers by the average number of pitches per batter faces.

Unfortunately, this type of pitch count information isn't known for most of baseball history. We know that the average number of pitches per batter was in the 3.6 to 3.8 range in the 1990s. And we know the rates of walks and strikeouts were at or near all-time highs in the 1990s, so it stands to reason that batters were seeing fewer pitches per plate appearance for most of baseball history. But how much lower is a matter of speculation. Our best estimate is that these rates have ranged from 3.1 to 3.8 over the course of the last hundred years.

Error rates

The error rates are expressed as the number of errors made per 100 games. We chose 100 games because the length of a season has changed over time, and we wanted a stable period of time to work with.

See Defensive Ratings for a table showing how error rates have changed over the past 100 years. You can use this table as a guide when choosing error rates for your own eras.

Pitch by pitch rates

The pitch-by-pitch rates govern how often a pitch results in a hit batsman, called ball, called strike, and so on. Click the Recalculate button to have DMB produce these values based on the era statistics that were entered on the General page.

These values have the following meaning:

• HBP rate. The number of pitches (per 10,000) that result in a hit batsman.

• Strike rate. The number of pitches (per 10,000) that result in a strike (called, swinging, foul ball, ball in play).

• Swing rate. The number of strikes (per 10,000) on which the batter swings.

• Foul rate. The number of swings (per 10,000) that produce a foul ball.

• In play rate. The number of swings (per 10,000) that produce a ball in play.

• Balk rate. The number of balks per 10,000 pitches with runners on base.

You can change the pitch-by-pitch rates, but it's not always easy to figure out the effect that your changes will have on your games. For example, increasing the In play rate will reduce the number of walks and strikeouts because more balls in play means that you won't have as many plate appearances that make it all the way to four balls or three strikes. But the amount by which it will reduce walks and strikeouts depends on the other pitch rates. An increase in the foul rate would reduce the number of strikeouts (by keeping the batter alive on more two-strike pitches) and increase the number of walks (because the batter may go on to draw walks where he might have already been struck out before). It's even harder to predict what will happen if you change more than one of these values at the same time.

Most of the time, the generated pitch-by-pitch rates will give you very accurate results. When we design season disks, we always start with these calculated rates. We occasionally make adjustments, but those adjustments are always small, and we often have to experiment by simulating the season a few times before we settle on a set of adjustments that gives us the results we're seeking.