Moneyball Labs

Funnel plot, year-to-year correlation

ERA minus FIP: luck, skill, or the fielders?

The gap between what a pitcher allowed and what his strikeouts, walks and home runs say he should have. A funnel shows how much of it is noise; last season shows how much carries over.

Computed on request from the record book (Oct 13, 2026) and 720 finals in the game log.

The finding

Among the 185 pitchers with 20 or more innings this season, ERA minus FIP ranges from −3.64 to +4.50 runs per nine. The funnel below shows the spread narrowing as innings pile up, at about the rate chance alone would produce — the widest gaps belong to pitchers with the fewest innings.

Last season is the sharper test. For the 67 pitchers who threw 40+ innings in both years, last year's gap predicts this year's at r = 0.14 (95% −0.10–0.37) — weak. A pitcher who beat his FIP last year is not reliably any more likely to do it again. Last year's FIP predicts this year's ERA at r = 0.25, last year's ERA at r = 0.17; re-centred for the change in league scoring, FIP misses this year's ERA by 1.27 runs per nine on average and ERA by 1.49. FIP is the better forecast, as the theory says, though with this many pitchers the two intervals overlap.

Gap repeats at

0.14

−0.10–0.37

FIP → next ERA

0.25

0.02–0.47

ERA → next ERA

0.17

−0.08–0.39

Pitchers compared

67

40+ IP both years

Small sample. 67 pitchers in both seasons. A correlation from this many has an interval about ±0.24 wide near zero.

The funnel: ERA minus FIP against innings

If the gap were pure noise, its spread would shrink with the square root of innings. The shaded bands are that shape (one and two standard deviations), scaled to the league as a whole.

±1 and ±2 SD of noisePitcher (team colour)
−4−20+2+450100150Kwak Bin: ERA 2.24, FIP 2.81, 161.0 IPKo Young-pyo: ERA 3.28, FIP 3.21, 172.7 IPJames Naile: ERA 3.49, FIP 3.67, 183.0 IPWes Benjamin: ERA 2.31, FIP 2.94, 132.7 IPAdam Oller: ERA 3.13, FIP 3.73, 178.0 IPWon Tae-in: ERA 4.52, FIP 3.35, 145.3 IPRyu Hyun-jin: ERA 3.88, FIP 3.39, 134.7 IPJeremy Beasley: ERA 4.96, FIP 3.72, 147.0 IPRaul Alcantara: ERA 3.87, FIP 3.86, 155.7 IPChoi Min-seok: ERA 3.20, FIP 3.75, 146.3 IPSo Hyung-joon: ERA 3.15, FIP 3.59, 131.3 IPPedro Avila: ERA 1.44, FIP 2.67, 93.7 IPAustin Reilly: ERA 2.69, FIP 3.66, 133.7 IPTolhurst: ERA 4.24, FIP 4.13, 163.3 IPAhn Woo-jin: ERA 3.54, FIP 3.33, 112.0 IPLim Chan-kyu: ERA 4.46, FIP 4.27, 169.7 IPWhite: ERA 3.98, FIP 3.95, 138.0 IPZach Logue: ERA 4.25, FIP 4.30, 165.3 IPHa Young-min: ERA 4.37, FIP 3.99, 134.0 IPElier Rodriguez: ERA 4.28, FIP 4.34, 159.7 IPPark Se-woong: ERA 4.64, FIP 4.25, 147.3 IPAriel Jurado: ERA 3.54, FIP 4.33, 150.0 IPKoo Chang-mo: ERA 4.03, FIP 4.51, 163.0 IPNa Kyun-an: ERA 4.27, FIP 4.41, 149.7 IPFedek: ERA 2.95, FIP 3.03, 76.3 IPChoi Won-tae: ERA 4.68, FIP 4.30, 125.0 IPOh Won-seok: ERA 5.58, FIP 3.98, 100.0 IPLee Young-ha: ERA 3.18, FIP 3.20, 68.0 IPDae Ni-el: ERA 2.13, FIP 2.61, 55.0 IPKim Jin-uk: ERA 4.12, FIP 4.70, 144.3 IPBo Schultz: ERA 3.16, FIP 3.15, 62.7 IPTaylor: ERA 4.78, FIP 4.61, 124.3 IPKim Min: ERA 3.36, FIP 3.41, 64.3 IPKa Ra-seu-ko: ERA 4.05, FIP 3.34, 60.0 IPLogan Allen: ERA 3.59, FIP 4.31, 92.7 IPBae Dong-hyun: ERA 6.28, FIP 4.16, 81.7 IPBae Dong-hyunKim Min-joon: ERA 3.56, FIP 4.38, 91.0 IPWang Yen-cheng: ERA 3.97, FIP 4.88, 133.7 IPKim Jae-yoon: ERA 3.22, FIP 3.75, 64.3 IPBae Je-sung: ERA 2.92, FIP 4.12, 77.0 IPTyler Wells: ERA 4.11, FIP 4.58, 96.3 IPLee Seung-min: ERA 2.65, FIP 4.02, 68.0 IPPark Si-won: ERA 3.79, FIP 3.77, 59.3 IPRyan O'Loughlin: ERA 4.86, FIP 4.43, 83.3 IPToda: ERA 5.03, FIP 5.08, 145.0 IPChoi Joon-yong: ERA 3.71, FIP 4.06, 60.7 IPCho Byeong-hyun: ERA 2.33, FIP 3.85, 54.0 IPPark Sang-won: ERA 4.80, FIP 3.77, 50.7 IPLee Ro-un: ERA 5.61, FIP 4.35, 69.0 IPYuta Sugimoto: ERA 5.90, FIP 4.42, 71.7 IPPark Young-hyun: ERA 2.48, FIP 4.18, 61.7 IPJeon Sang-hyun: ERA 2.33, FIP 3.68, 46.3 IPCho Dong-uk: ERA 4.31, FIP 4.12, 56.3 IPYang Chang-seop: ERA 5.00, FIP 4.86, 93.7 IPSung Young-tak: ERA 3.47, FIP 4.20, 57.0 IPYuto Takahama: ERA 5.19, FIP 4.03, 50.3 IPBo Seu: ERA 4.80, FIP 2.75, 30.0 IPWon Jong-hyun: ERA 6.19, FIP 3.97, 48.0 IPTakada: ERA 3.21, FIP 4.19, 53.3 IPMatt Sauer: ERA 4.88, FIP 5.02, 101.3 IPKim Taek-yeon: ERA 2.54, FIP 4.33, 56.7 IPChoi Seung-yong: ERA 6.47, FIP 5.14, 114.0 IPPark Chi-kook: ERA 5.40, FIP 4.07, 48.3 IPKim Won-joong: ERA 4.91, FIP 4.40, 58.7 IPKim Jung-woo: ERA 2.28, FIP 4.43, 59.3 IPYang Hyeon-jong: ERA 4.19, FIP 5.22, 124.7 IPKim Young-woo: ERA 4.17, FIP 3.97, 45.3 IPCho Sang-woo: ERA 3.29, FIP 4.55, 63.0 IPJang Hyun-sik: ERA 4.02, FIP 4.32, 53.7 IPSon Ju-young: ERA 3.22, FIP 4.23, 50.3 IPTakeda: ERA 7.41, FIP 5.08, 98.3 IPTakedaPark Joon-hyun: ERA 5.75, FIP 4.99, 87.7 IPKazuki Iimura: ERA 6.11, FIP 3.61, 35.3 IPPark Jung-min: ERA 3.66, FIP 4.55, 59.0 IPLee Tae-yang: ERA 2.55, FIP 3.64, 35.3 IPKo Woo-seok: ERA 1.57, FIP 2.47, 23.0 IPLee Sang-kyu: ERA 5.19, FIP 4.59, 59.0 IPRyosuke Shirakawa: ERA 4.75, FIP 5.03, 83.3 IPBae Jae-hwan: ERA 4.93, FIP 4.40, 49.3 IPHyun Do-hoon: ERA 4.67, FIP 4.55, 52.0 IPLee Geon-uk: ERA 3.13, FIP 4.40, 46.0 IPZach Rosenberg: ERA 4.80, FIP 3.59, 30.0 IPElieser Hernandez: ERA 4.92, FIP 4.95, 71.3 IPWoo Gang-hoon: ERA 5.30, FIP 4.62, 52.7 IPHatch: ERA 6.02, FIP 4.22, 40.3 IPKwak Do-kyu: ERA 2.81, FIP 3.80, 32.0 IPJeon Yong-ju: ERA 4.37, FIP 4.43, 45.3 IPLim Gi-young: ERA 4.74, FIP 4.75, 57.0 IPWhite: ERA 4.11, FIP 3.75, 30.7 IPHan Du-sol: ERA 5.59, FIP 4.15, 37.0 IPChoi Ji-gwang: ERA 2.45, FIP 3.01, 22.0 IPSon Dong-hyun: ERA 3.57, FIP 4.92, 63.0 IPPark Jung-hoon: ERA 5.71, FIP 4.86, 58.3 IPSong Seung-gi: ERA 5.53, FIP 5.04, 70.0 IPLee Min-woo: ERA 4.74, FIP 4.83, 57.0 IPJung Hae-young: ERA 6.12, FIP 4.73, 50.0 IPLee Joon-hyuk: ERA 2.78, FIP 4.28, 35.7 IPPark Jin-hyung: ERA 4.10, FIP 4.44, 37.3 IPKim Tae-hoon: ERA 2.48, FIP 4.55, 40.0 IPLee Woo-chan: ERA 3.29, FIP 3.92, 27.3 IPLee Seung-hyun: ERA 6.25, FIP 4.76, 44.7 IPKim Jin-su: ERA 3.84, FIP 5.08, 61.0 IPKim Min-su: ERA 5.70, FIP 4.72, 42.7 IPKim Sung-jin: ERA 6.25, FIP 4.69, 40.3 IPYoon Tae-ho: ERA 3.65, FIP 3.92, 24.7 IPWoo Kyu-min: ERA 3.35, FIP 4.72, 40.3 IPLee Jin-ha: ERA 2.74, FIP 3.81, 23.0 IPKe Ne-di: ERA 3.80, FIP 3.93, 23.7 IPLee Yong-joon: ERA 3.81, FIP 4.13, 26.0 IPLee Min-seok: ERA 6.19, FIP 5.04, 52.3 IPJoo Kwon: ERA 4.25, FIP 5.06, 53.0 IPDrew VerHagen: ERA 4.68, FIP 4.11, 25.0 IPLee Byeong-heon: ERA 5.44, FIP 4.92, 44.7 IPLee Jung-yong: ERA 7.31, FIP 5.14, 56.7 IPKim Jin-sung: ERA 4.94, FIP 4.99, 47.3 IPCollin Wiles: ERA 5.40, FIP 4.15, 25.0 IPCushing: ERA 4.79, FIP 3.79, 20.7 IPLee Seung-hyun: ERA 6.02, FIP 4.94, 43.3 IPJang Yu-ho: ERA 3.38, FIP 5.07, 45.3 IPSon Ju-hwan: ERA 7.45, FIP 4.97, 38.7 IPKim Jung-un: ERA 3.12, FIP 4.55, 26.0 IPKang Jae-min: ERA 4.44, FIP 4.58, 26.3 IPLim Ji-min: ERA 5.40, FIP 5.18, 46.7 IPJeon Sa-min: ERA 5.43, FIP 5.41, 63.0 IPHan Seung-hyuk: ERA 6.68, FIP 4.91, 32.3 IPChoi Min-joon: ERA 4.91, FIP 5.64, 102.7 IPHong Min-kyu: ERA 7.59, FIP 4.49, 21.3 IPOh Seok-ju: ERA 5.47, FIP 4.69, 24.7 IPChirinos: ERA 6.68, FIP 5.04, 33.7 IPKim Tae-hyung: ERA 4.99, FIP 5.56, 79.3 IPKim Beom-su: ERA 5.63, FIP 5.25, 40.0 IPYang Jae-hoon: ERA 5.92, FIP 4.83, 24.3 IPMoon Seung-won: ERA 3.45, FIP 5.52, 62.7 IPCho Young-geon: ERA 4.50, FIP 5.31, 42.0 IPHwang Joon-seo: ERA 5.51, FIP 5.53, 63.7 IPJung Chul-won: ERA 6.75, FIP 5.05, 28.0 IPKwon Min-kyu: ERA 4.43, FIP 4.73, 20.3 IPKim Gang-hyun: ERA 4.50, FIP 4.87, 22.0 IPAnthony Benigiano: ERA 6.10, FIP 5.67, 79.7 IPShin Young-woo: ERA 2.86, FIP 5.40, 34.7 IPHam Deok-ju: ERA 6.19, FIP 5.43, 32.0 IPJang Chan-hee: ERA 4.50, FIP 5.75, 76.0 IPChoi Joon-ho: ERA 4.30, FIP 5.34, 23.0 IPMoon Dong-ju: ERA 5.18, FIP 5.40, 24.3 IPPark Sin-ji: ERA 6.37, FIP 5.59, 35.3 IPHan Jae-seung: ERA 4.50, FIP 5.65, 42.0 IPKim Tae-kyung: ERA 5.76, FIP 5.67, 45.3 IPLee Hyung-beom: ERA 4.15, FIP 5.56, 30.3 IPLee Yong-chan: ERA 4.20, FIP 5.73, 45.0 IPKim Young-kyu: ERA 3.92, FIP 5.58, 20.7 IPJim Meo-maen: ERA 10.23, FIP 5.73, 31.7 IPJim Meo-maenYoon San-heum: ERA 5.73, FIP 5.78, 22.0 IPPark Joon-young: ERA 6.06, FIP 5.89, 71.3 IPKim Geon-woo: ERA 6.38, FIP 5.92, 132.7 IPBae Chan-seung: ERA 2.25, FIP 5.89, 44.0 IPBae Chan-seungKim Yoon-sik: ERA 6.11, FIP 5.96, 35.3 IPJeon Joon-pyo: ERA 4.29, FIP 6.00, 65.0 IPKeul Re-bin-jeo: ERA 3.74, FIP 6.14, 21.7 IPWon Jong-hae: ERA 6.14, FIP 6.11, 29.3 IPJung Woo-ju: ERA 8.02, FIP 6.05, 46.0 IPJeon Young-joon: ERA 5.56, FIP 6.04, 56.7 IPLee Ui-ri: ERA 6.68, FIP 6.05, 63.3 IPShin Min-hyuk: ERA 4.79, FIP 6.13, 35.7 IPJoo Hyun-sang: ERA 5.87, FIP 6.25, 23.0 IPPark Si-hoo: ERA 6.17, FIP 6.10, 46.7 IPKim Sun-gi: ERA 6.12, FIP 6.31, 25.0 IPBae Jae-joon: ERA 10.54, FIP 6.30, 27.3 IPBae Jae-joonChoi Ji-min: ERA 7.36, FIP 6.23, 36.7 IPHwang Dong-ha: ERA 5.03, FIP 6.08, 93.0 IPPark Ji-sung: ERA 4.40, FIP 6.23, 47.0 IPKim Jae-woong: ERA 9.30, FIP 6.75, 20.3 IPLee Sang-dong: ERA 7.23, FIP 6.64, 23.7 IPNoh Kyung-eun: ERA 4.72, FIP 6.36, 47.7 IPShota Miyaji: ERA 5.87, FIP 6.65, 30.7 IPRyu Jin-uk: ERA 8.72, FIP 6.68, 32.0 IPKang Geon-woo: ERA 8.74, FIP 6.99, 22.7 IPBaek Jung-hyun: ERA 7.30, FIP 7.00, 24.7 IPKim Seo-hyun: ERA 6.92, FIP 7.05, 26.0 IPSong Myeong-gi: ERA 6.75, FIP 6.71, 38.7 IPJung Hyun-woo: ERA 9.90, FIP 7.60, 20.0 IPKim Jong-su: ERA 6.63, FIP 6.91, 36.7 IPJung Da-hoon: ERA 6.11, FIP 7.27, 28.0 IPKim Jin-ho: ERA 6.15, FIP 6.91, 45.3 IPKim Yoon-ha: ERA 6.83, FIP 7.75, 27.7 IPPark Joon-young: ERA 7.56, FIP 7.33, 50.0 IPInnings pitchedERA − FIP
6 of 185 pitchers fall outside the 95% band; about 9 would if the gap were noise. Above zero: ERA worse than FIP.

What carries from one season to the next

Correlation between last season's number and this season's, for the same pitchers, with 95% intervals.

0.00.51.0ERA → next ERA0.17FIP → next ERA0.25FIP → next FIP0.36ERA − FIP → next gap0.14Pearson r

Method

FIP = (13·HR + 3·(BB + HBP) − 2·K) ÷ IP + C

FIP is computed the same way as on the player pages, with the constant C solved from each season's own totals so that league FIP equals league ERA. The funnel's band assumes the gap's variance falls as c ÷ IP and sets c = 69.6 from all 185 pitchers, so it shows the shape noise would take rather than testing against an outside standard. The carry-over correlations match pitchers by their record-centre ID across the 2025 and 2026 snapshots; intervals use Fisher's z transformation, and the gap's correlation has p = 0.25.

ERA minus FIP is not all luck. It holds the defence behind the pitcher, his park, how the bullpen handled the runners he left on base, and any real skill at limiting hard contact — none of which the KBO's public data separates. The year-to-year comparison only includes pitchers who kept a job for two seasons, which leans toward the better ones.