Publication:

日本職棒打者表現與年齡分析

職業球團與球員簽訂合約的金額與年限，以及球員交易，都需要預測球員未來的表現。目前職業球團普遍使用的方法，是根據該球員前幾年的表現，因此需要更明確的評估方式，用來預測球員未來的表現。已有數個研究針對美國職棒大聯盟，探討球員表現隨年齡的變化，但仍缺乏日本職棒相關研究，且台灣球員與日本球員體型、人種較接近，日本之情況可做為台灣參考。本研究目的為根據日本職棒打者四項修正後的數據:打擊率、純長打率、三壘安打率及二壘加三壘安打率，以及未修正之四壞球保送率，探討日本職棒打者生涯表現隨年齡改變的趨勢。研究對象為日本職棒1980至2010年間，每年球季至少累積擁有200打席，並且至少出賽8年以上的打者。為了將不同年代打者的表現都放在同一基準點做比較，本研究以日本職棒上述各項成績根據當年的聯盟平均數據標準化後，分析各項數據隨年齡改變的趨勢。結果發現，打擊率的生涯顛峰年齡位於26至29歲；四壞球保送率位於31歲；純長打率位於26至28歲；三壘安打率位於26至27歲；二壘加三壘安打率位於26至28歲。日本職棒高打擊率的打者，通常會附帶著較佳的純長打率、三壘安打率及二壘加三壘安打率，生涯表現也相對穩定；四壞球保送率方面，選球能力好的打者，會伴隨較佳的打擊率、純長打率及二壘加三壘安打率；純長打率方面，並不因年齡的增長而衰退，反而呈現上升的現象，具有純長打能力的打者，大都具備著優異的打擊率、四壞球保送率及二壘加三壘安打率；三壘安打率方面，具有速度的打者，在打擊率與二壘加三壘安打率的表現上佔有優勢；二壘加三壘安打率方面，高於聯盟平均的打者，在各方面的表現都比較出色。而兼具兩種能力的打者，通常在各方面的表現都不錯。透過本研究，希望可更客觀的評估日本職棒球員年齡與各項表現的關係，提供球團在簽訂球員合約，以及進行球員交易的參考，同時可做為台灣棒球發展的參考。

The prediction of performance for professional baseball players is required in determining the length and the amount of contracts and trades. The method which teams generally use at present is based on the player’s performance in previous years. Therefore, a more reliable method is required to predict the future performance of the players. There are several studies investigating the performance changes with age in Major League Baseball. There is no study examining the aging effect in performance in Nippon Professional Baseball. The baseball players in Japan and Taiwan have similar body type and genetic background. Therefore, the results from, Nippon Professional Baseball could be used as a reference for Chinese Professional Baseball League. The purpose of this research is to analyze the trend of career performance changes with age in Nippon Professional Baseball. This study used four adjusted statistics: batting average, isolated power, triples percentage, and doubles plus triples percentage, and unadjusted base on balls percentage as the indicators for performance. The subjects included Nippon Professional Baseball hitters who have played at least eight years and had 200 or more plate appearances in each year. In order to compare the hitters from different era, this study normalized the yearly numbers to the league average of that category in the specific year. The results showed that the highest batting average occurred between 26 to 29 years old; the highest base on balls percentage occurred in 31 years old; the best isolated power occurred between 26 to 28 years old; the highest triples percentage occurred between 26 to 27 years old; and highest doubles plus triples percentage occurred between 26 to 28 years old. The hitters with high batting average also showed good isolated power, triples percentage and doubles plus triples percentage. The players with good base on balls percentage also showed high batting average, isolated power and doubles plus triples percentage. The hitters with good isolated power also showed high batting average, base on balls percentage, and doubles plus triples percentage. The hitter with high triples percentage also showed high batting average and doubles plus triples percentage. The players with high doubles plus triples percentage showed higher performance in all other categories. The hitters with high performance in two categories were also good at other categories. The results of this study could provide a more objective prediction of aging effect in hitting performance in Nippon Professional Baseball. These information can be used in contract negotiations and served as the reference for the development of professional baseball in Taiwan.