Chapter 3 of 11
Stolen bases and the break-even rate
A steal is a bet with known odds. The base gained is worth less than the runner lost, so you have to win the bet often.
The short version
Run only when your chance of being safe clears the break-even line for that base, those outs and that score.
KBO 2026 season data through Oct 13, 2026
01
The idea
A stolen base is a bet. Win it and the runner is ninety feet closer; lose it and he is gone, and an out with him. Because the loss is bigger than the gain — an out and a baserunner against a single base — the bet only pays if you win it most of the time.
How often is “most”? That depends on the base, the outs and the score, and the answer is the break-even rate: the success rate at which running and standing still are worth exactly the same.
02
The math
break-even = (V(stay) − V(caught)) ÷ (V(safe) − V(caught))
Example: runner on first, nobody out — 0.97 standing still, 1.20 if safe, 0.30 if caught. Break-even 74.6%.
Three routes to the same figure agree closely. The simulated table gives 75% for second base with nobody out; the lab's matrix gives 72%; and the linear weights the platform uses for baserunning value (a steal worth +0.20 runs, a caught stealing −0.41) imply 67% across all situations.
| Steal of | Early: runs | Chance of a run | Tied, top 9th | Tied, bottom 9th |
|---|---|---|---|---|
| Second, nobody out | 75% | 57% | 61% | 57% |
| Second, one out | 74% | 57% | 62% | 57% |
| Second, two out | 69% | 54% | 58% | 54% |
| Third, nobody out | 81% | 68% | 72% | 68% |
| Third, one out | 73% | 61% | 64% | 61% |
| Third, two out | 92% | 89% | 90% | 89% |
Two patterns stand out. Stealing third with one out is cheaper than its reputation, because a runner on third with one out scores on so many kinds of out. Stealing third with two out is a bad bet almost everywhere: the runner on second already scores on most singles, so the base gained adds little, and the out ends the inning.
03
Try it
| Yardstick | Hold the runner | Send him | Change | Break-even success rate |
|---|---|---|---|---|
| Expected runs | 0.97 | 0.97 | +0.00 | 75% |
| Chance of a run | 43.7% | 52.2% | +8.5 | 57% |
With first and second it is a double steal; with first and third the runner on first goes. On a failure the lead runner is out. Win value is a win plus half a tie.
04
This season in the KBO
Stolen bases
900
Caught
309
Success rate
74.4%
Attempts per team game
0.84
The league as a whole is running at 74.4%, just below the 75% break-even for second base with nobody out; 4 of ten clubs clear that line. That is a sign of running too much, not too little. A team that sends runners only when the odds are good should succeed well above break-even on average, because its last, most marginal attempt is the one that sits at break-even. An average on the line means plenty of attempts below it.
Attempts per team game
Success rate
The seasons the platform holds. Teams ran more often in 2010 and less successfully; the modern league runs less and wins the bet far more.
| Most attempts | SB | CS | Success |
|---|---|---|---|
| Hwang Sung-bin Lotte | 55 | 11 | 83% |
| Park Min-woo NC | 50 | 12 | 81% |
| Park Hae-min LG | 42 | 17 | 71% |
| Park Chan-ho Doosan | 33 | 8 | 80% |
| Choi Won-joon KT | 28 | 12 | 70% |
| Kim Ju-won NC | 30 | 9 | 77% |
| Ryu Ji-hyuk Samsung | 29 | 6 | 83% |
| Choi Jung-won NC | 25 | 8 | 76% |
05
When the conventional wisdom is wrong
01
“Speed changes the game”
A steal is worth about a fifth of a run; a caught stealing costs twice that. Thirty steals at an 80 percent clip is worth about three runs over a season; at 70 percent, less than one. Speed matters most in going first to third and scoring from second, which the record does not capture.
02
Two-out steals late can pay
With two out in a tied ninth, a runner on second scores on most singles and a runner on first does not. When one run wins, the break-even for second base with two out drops — the table above shows by how much.
03
Never run your best hitter into an out
The tables assume a league-average hitter at the plate. With a slugger up, standing still is worth more, and the break-even rises. The same steal is a better bet with the bottom of the order batting.
04
The clock helps the runner
A pitch clock and a cap on pickoff throws take tools away from the pitcher. In MLB, the 2023 rule changes pushed league success rates to around 80 percent. Chapter eleven looks at what the KBO's clock did.
Steals and caught stealing are summed from the hitters' lines; pickoffs and steals of home are not split out, and the KBO does not publish which base was stolen, so the season's figures are all bases together. Catchers' throwing records are not in the season files.