CPBL To Lower COR Value of Baseball in 2021 Season

CPBL to De-Juice Its Baseball in 2021

On September 24, the CPBL decided to further de-juice the baseball in the 2021 season. According to the league, the ball’s COR value will go down from .560 to .550 as per teams’ request.

COR stands for coefficient of restitution, to put it in a layman’s term, the number represents the energy retained upon the initial impact. Higher the COR value, the ball will travel further in the air.

In the past, the CPBL team owners decided to set the COR value between .550 to .570. However, in the first half of the 2020 season, the league failed at doing their job and eventually led to the juiced ball scandal.

The balls were sent to the lab for testing, but both batches came back exceeding the COR standard at .571 and .574.

Due to the public pressure, the league deiced to change the ball in mid-season. The CPBL reproduced a new batch of balls with a COR value at .560 and began to use that in the second-half season.

Below is a table showing changing the COR value of the ball will affect the league’s average hitting and pitching stats. The second-half season data is as of September 25.

Projected Hitting Stats With .550 COR

Below are some charts compiled by pokerwu from Taiwanese baseball online community. Using the information available online, He plotted the COR values and the hitting stats in the past ten years to project the hitting stats for the 2021 season.

COR Values: CPBL vs MLB, NPB and KBO

The MLB is reportedly keeping their ball COR value between 0.514 to 0.578. Both MLB and CPBL are using the same testing method.

Japan’s NPB and Korea’s KBO, on the other hand, are using a different testing method, their COR value is between 0.403 to 0.423. You can not compare NPB and KBO COR value with the MLB and CPBL’s COR value.

  • CPBL – 0.550 (2021 Season)
  • MLB – 0.514 to 0.578
  • NPB – 0.403 to 0.423 (Different testing method than CPBL and MLB)
  • KBO – 0.403 to 0.423 (Different testing method than CPBL and MLB)


  1. Actually, offense has been about right in the second half. CPBL has long been a hitters’ league, and it would a mistake to cut down offense too much. Causal fans want to see the ball getting hit.

    • My personal opinion, I think it is still a bit too high. But it is almost at the sweet spot. I prefer if they set the medium line around .555

      I think the league want to control the league average OPS to around .700 to .750 and also make the ball have the same COR as the new KBO de-juiced ball.

      There’s rumour, the KBO new COR once converted is roughly .550 to .555.

    • For KBO, I think the reason is more got something to do with public perception of a few KBO players using the Asian Games to avoid the 2 years mandatory military service and the public image of the Heroes owner going to jail. Also, the overall standings were not that tight in 2018 as well.

      Their attendance eventually will hit a plateau, because their market at this stage can only support that much, it would be unrealistic to have that much gain in attendance year by year.

      As for the CPBL de-juiced ball, I think it will be fine. Your typical home run hitters are still going to hit bombs. This will just eliminate those who have no business at hitting homers.

      In my opinion, COR .555-ish is much fairer to both pitchers and batters. Domestic pitchers can develop better with a normal ball.


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