Factor 1: It takes more pitches to complete a no-hitter than ever before.
This season, batters are making pitchers throw a record 3.93 pitches per
plate appearance, up from 3.89 last year, 3.83 in 2015 and 3.74 in the early
2000s. Outs take more pitches than hits, and strikeouts take more pitches
than other outs, and strikeouts are a bigger percentage of outs than they've
ever been. For that matter, walks (which take the most pitches of all) are
much more common than they've been in any season since 2000.
原因一:
現在要完成一場無安打比賽，需要用比以往更多的球。這季的打者，讓投手在每個
打席的用球數，比起去年的3.89顆、2015年的3.83顆、2000年初的3.74顆，上升到
3.93顆。出局比安打需要更多的用球數，三振又比其他的出局方式需要更多的用球數，
比起以前，當今三振數佔了出局數的最大宗。而且，現在的保送（所有打席中，需要
最多的用球數）比2000年開始的任一年都還要來的普遍。
If we look at all the games in which a team threw nine innings and allowed no
hits or one hit, the number of pitches required to get the 27 outs has been
steadily rising. In the 1990s, the median pitch count in these games was 114.
In the 2000s, it was 115, in the first half of this decade it was 117, and in
2016-2017 it was 120. This year, the median is 125 pitches. Most of those are
one-hitters, so knock off three or four pitches from those averages to
reflect one fewer batter, but the rise is real.
如果我們檢視歷年來，當一隻球隊投出九局無安打或一安打的所有比賽，要抓下27個
出局數所用的球數，正在穩定的逐年提高中。在1990年，這類型的比賽用球數的中位數是
114球。到了2000年，已經變成115球。在2011到2015年，則是117球，16到17年則是變成
120球。至於今年，已經來到125球。這些比賽大部分都是一安打的比賽，所以從先前
提到的用球數中位數減去3或4球後，來作為無安打比賽所需要的用球數（因為一個打數
的用球數，大概是3或4球差不多）。用球數真的正在逐年提高中。
Factor 2: The occurrences of 120-pitch starts have gotten really rare. We all
know that teams are more sensitive about pitch counts, and that on average
pitchers get pulled from games earlier than ever. But it's not just on
average: On the extremes, in the very best starts, teams are far less likely
to let a pitcher go deep. Last season, 95 percent of starters were pulled at
110 pitches or fewer. Just seven years ago, the 95th percentile pitch count
was 117, and in 2000 it was 124