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:
现在要完成一场无安打比赛，需要用比以往更多的球。这季的打者，让投手在每个
打席的用球数，比起去年的3.89颗、2015年的3.83颗、2000年初的3.74颗，上升到
3.93颗。出局比安打需要更多的用球数，三振又比其他的出局方式需要更多的用球数，
比起以前，当今三振数占了出局数的最大宗。而且，现在的保送（所有打席中，需要
最多的用球数）比2000年开始的任一年都还要来的普遍。
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.
如果我们检视历年来，当一只球队投出九局无安打或一安打的所有比赛，要抓下27个
出局数所用的球数，正在稳定的逐年提高中。在1990年，这类型的比赛用球数的中位数是
114球。到了2000年，已经变成115球。在2011到2015年，则是117球，16到17年则是变成
120球。至于今年，已经来到125球。这些比赛大部分都是一安打的比赛，所以从先前
提到的用球数中位数减去3或4球后，来作为无安打比赛所需要的用球数（因为一个打数
的用球数，大概是3或4球差不多）。用球数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