SLG & ISO: hits are not created equal
Why can a .260 hitter be scarier than a .300 hitter?
Slugging percentage fixes AVG's other blind spot: it weights hits by bases. A single is 1, a double 2, a triple 3, a homer 4 — total bases divided by at-bats. Doubles and homers move runners and score runs in a way singles can't.
ISO: power distilled
SLG still contains all those singles, so a high-AVG slap hitter can post a decent SLG without real power. Subtract AVG from SLG and the singles vanish: what's left — isolated power — counts only the extra bases. ISO .100 is a singles hitter; .200 is real power; .250+ is a slugger.
Caveat before you fall in love: SLG's weights are wrong. A homer is not worth exactly four singles — real run values (Level 3) say it's worth about three. SLG is a good sketch of power, drawn with slightly crooked lines.
The formula (optional — skippable)
SLG = Total Bases ÷ AB ISO = SLG − AVG
How this stat lies to you
- Its 1/2/3/4 weights overrate extra-base hits relative to real run values.
- It ignores walks completely, just like AVG.
- A high SLG on a huge AVG can hide mediocre power — check ISO to be sure.
Check yourself
1. Player A: AVG .310, SLG .420. Player B: AVG .250, SLG .500. Who has more power?
2. What does ISO remove from SLG?