Terminology

 "Equity"

 From: Gary Wong Address: gary@cs.arizona.edu Date: 25 December 1998 Subject: Re: Please Explain Equity Forum: rec.games.backgammon Google: wthfuk3sgd.fsf@brigantine.CS.Arizona.EDU

```Craig Yannuzzi writes:
> Can someone please explain how to interpret Equity numbers for various
> moves.

There is a precise definition of equity and some discussion on Backgammon
Galore at:

http://www.bkgm.com/gloss/lookup.cgi?equity

Another good description is this one by Robertie (_Advanced Backgammon_
vol 2, position 357):

"_Equity_ is a fundamental concept of backgammon, indeed of any game
which is a mixture of skill and chance.  The equity of a position is
the average profit (or loss) that one would net, per game, by playing
the position to conclusion an infinite number of times.  It is the
`value' of the position."

Equity may appear somewhat obscure at first, but it really is a very
natural way of measuring the strength of a position.  The unit of measure
is "points per game" (ppg) which has a very intuitive interpretation:
suppose the cubeless equity in a particular position is estimated at
-0.247.  That means we expect to lose 0.247 points per game -- if we played
1000 games for \$1 a point with no cube starting from that position, we
would expect to lose \$247.

> Why are the numbers negative...

We all try very hard _not_ to make the numbers negative :-)  Since one
player loses exactly as much as the other player wins (backgammon is a
"zero sum" game), if the equity is positive for one player then it will
be negative for the other.  If the equity is positive then you're winning;
if it's negative then you're losing.

> ...with the highest number best?

The higher number is best simply because you expect to win more!  Sometimes
I've seen posts arguing "a move isn't better because the equity is greater;
the equity is greater because the move is better", but I think it's
pointless trying to impose any cause and effect here.  That would be like
saying "You're not taller than me because your height is greater; your
height is greater because you're taller than me."  They are exactly
equivalent; you can't have one without the other; and if you try to
separate the two then you're not doing justice to either.  As Robertie
writes:

"...You are not, of course, mentally comparing two numbers; you are
choosing whichever position looks better.  The process of your backgammon
education is properly linking `looking better' with `higher equity'."

Cheers,
Gary.
--
Gary Wong, Department of Computer Science, University of Arizona
gary@cs.arizona.edu     http://www.cs.arizona.edu/~gary/
```

### Terminology

Alphabet soup  (Tom Keith, Apr 2004)
"Anchor and guard" position  (Chase+, Apr 2010)
"Back game"  (Marty Storer, Jan 2004)
"Baffle box"  (garyo+, Mar 2005)
"Bagai position"  (Timothy Chow, Dec 2012)
"Banana split"  (Rich Munitz+, June 2011)
"Banana split"  (Adam Stocks+, Sept 2004)
"Beavers"  (Sander van Rijnswou, May 1999)
"Beavers"  (Shuman Lloyd Lee, Aug 1991)
"Blunder", "whopper"  (Raccoon+, July 2005)
"Bot"  (Pit Bull+, Mar 2004)
"Bronstein" clock setting  (rew+, Sept 2012)
"Calcutta auction"  (Roland Scheicher+, Dec 2001)
"Chouette"  (Roland Scheicher+, Mar 2002)
"Cube provocation play"  (Chuck Bower+, Apr 2007)
"Dance"  (William R. Tallmadge, May 1998)
"Dropper"  (Robert D. Johnson, Sept 1996)
"Duplication" and "diversification"  (Simon Woodhead, Nov 1991)
"Equity"  (Gregg Cattanach, Aug 2000)
"Equity"  (Gary Wong, Dec 1998)
"Equity"  (Chuck Bower, Oct 1996)
"Equity"  (Michael J. Zehr, Mar 1996)
"Equity", "volatility", "claim", "market"  (Erik Gravgaard, June 1995)
"Freeroll"  (montygram, Nov 2005)
"Gammon price"  (Ron Karr, Aug 1996)
"Gammon rate", "gammon price"  (David Montgomery, June 1995)
"Gammon-go" (GG) and "gammon-save" (GS)  (Mary Hickey, Feb 2004)
"Gammon-go" (GG) and "gammon-save" (GS)  (Marty Storer, Oct 2002)
"Gammon-go" (GG)   (Chuck Bower, Jan 2004)
"Golden point"  (Daniel Murphy, Dec 2004)
"Holding game"  (Alan Webb+, Dec 1998)
"In the box"  (Ken Bame+, Sept 2012)
International phrase dictionary  (David Allen Sorensen, Sept 1997)
"Joker"  (Richard Divdesman, Sept 1998)
"Kamikaze play"  (Bill Patterson+, June 2011)
"Kauder paradox"  (Carl Tait+, Nov 1995)
"Latto paradox"  (Jean-Pierre Seiman+, July 2004)
"Lose your market"  (Shuman Lloyd Lee+, Aug 1991)
"PRaT"  (Raccoon+, Jan 2007)
"Phantom double hit"  (Marty Storer, May 2010)
"Polish prime"  (Jason Lee+, Jan 2006)
"Pure play"  (Daniel Murphy, Nov 2000)
"Pure play"  (Casey Forrest+, Feb 1996)
"Raccoon"  (Steven Keats, Feb 2011)
"Root number"  (Ken Bame, June 2004)
"Russian Bridges"  (leobueno+, Mar 2013)
"Short play"  (AJ+, July 2012)
"Speed board"  (Gregg Cattanach, June 2004)
"Splot"  (mamabear, Apr 2007)
"Squeeze", "trap play"  (Philippe Michel+, Feb 1997)
"Suicide play"  (Brian Sheppard, Aug 1997)
"Swing tournament"  (Carlo Melzi+, Mar 2006)
"Table stakes"  (Carlo Melzi, Sept 2002)
"Technical play"  (Adam Stocks+, July 2002)
"Thematic"  (Beauregard+, Aug 2009)
"Thorp count"  (Stephen Turner, June 1996)
"Time," "timing," "checker," "dancing"  (Marty Storer, Apr 1992)
Turkish names for rolls  (Lars Soezueer, Mar 1997)
"Vigorish"  (Anthony R Wuersch, Feb 1995)
"Volatility"  (Michael J. Zehr, June 1998)
"Wash"  (Hardy Hübener+, Sept 2004)
"Wash"  (Brian Sheppard, July 1997)
"Weaver"  (Alan Webb+, May 2000)
"Zone" of attack  (Matt Reklaitis+, Dec 2007)