**Assists (A). **Awarded to a pitcher on a
strikeout from 1885 to 1888, but changed retroactively to
reflect modern scoring rules.
**Assists per 162 Games (A/162). **Calculated as
(assists times 162) divided by games. If innings played
are available, a more accurate calculation is (assists
times nine times 162) divided by innings played. See
Evaluating Fielding.

**At-Bats (AB). **Included bases on balls in 1876
and 1887, but changed retroactively to reflect modern
scoring rules. Included sacrifice hits from 1889 to 1893
and sacrifice flies from 1931 to 1938 and 1940 to
1953.

**Balks (Bk). **Available for most seasons in
major-league history from a combination of official and
reconstructed sources.

**Baserunners per Nine Innings Pitched (BR/9). **A
pitching statistic. Calculated as [(hits plus bases
on balls plus hit batsmen) times nine] divided by
innings pitched. Hit batsmen are omitted if
unavailable.

**Bases on Balls (BB). **Counted as at-bats in 1876
and as at-bats and hits in 1887, but changed
retroactively to reflect modern scoring rules. Until the
present standard of four balls was permanently adopted in
1889, the number of balls required for the batter to be
awarded first base varied: nine balls from 1876 to 1879,
eight balls in 1880 and 1881, seven balls in 1882, 1883,
and 1886, six balls in 1884 and 1885, and five balls in
1887 and 1888. Until 1887, a batter could specify a
strike zone above or below the waist.

**Bases on Balls per Nine Innings Pitched (BB/9).
**A pitching statistic. Calculated as (bases on balls
times nine) divided by innings pitched.

**Bases on Balls Percentage (BB%). **A batting
statistic. Calculated as bases on balls divided by
(at-bats plus bases on balls).

**Batters Facing Pitcher (BFP). **The sum of
at-bats, bases on balls, hit batsmen, sacrifice hits, and
sacrifice flies against a pitcher. Recorded by the
National League since 1903 and the American League since
1908. Available for all seasons in major-league history
from a combination of official and reconstructed
sources.

**Batters' Park Factor (BPF). **Can be expressed as
a whole number (100) or as a decimal (1.00). The extent
to which a batter's statistics benefited or suffered from
the ballparks in which his team played its games.
Includes not only the differences between his home park
and the road parks in which his team played, but also an
adjustment for the fact that the batter did not have to
face his own team's pitchers. Generally, an average park
factor is 100, a park factor indicating a hitters' park
is greater than 100, and a park factor indicating a
pitchers' park is less than 100. Park factors are the
same as those provided by *Total Baseball* and are
based on three-year averages. For more on park factor,
refer to the *Total
Baseball* glossary.

**Batting Average (Avg). **Calculated as hits
divided by at-bats.

**Batting Runs (BR).** Calculated as (0.47 times
singles) plus (0.78 times doubles) plus (1.09 times
triples) plus (1.40 times home runs) plus (0.31 times
(bases on balls plus hit by pitch plus stolen bases minus
caught stealing)) minus (0.276 times (at-bats minus hits
plus caught stealing). An estimate of a batter's total
individual contribution to his team in terms of runs
above or below the league average, assuming the same
number of outs. Zero indicates a league-average batter, a
positive total indicates an above-average batter, and a
negative total indicates a below-average batter. In order
to adjust for park factor, calculate as (0.47 times
singles) plus (0.78 times doubles) plus (1.09 times
triples) plus (1.40 times home runs) plus (0.31 times
(bases on balls plus hit by pitch plus stolen bases minus
caught stealing)) minus (0.276 times batters' park factor
times (at-bats minus hits plus caught stealing).
Developed by Pete Palmer. For more on batting runs, refer
to the *Total
Baseball* glossary. See also Evaluating
Batting.

**Batting Runs Beyond Position (+Pos).** Calculated
as batter's batting runs minus (position-average batting
runs times batter's outs made divided by position-average
outs made), where outs made is at-bats minus hits plus
caught stealing. An estimate of the number of batting
runs the batter contributed above or below the average of
starters at his position given the same number of
outs.See Evaluating
Batting.

**Caught Stealing (CS). **Adopted officially by
both leagues in 1920, but dropped by the National League
after 1925 and not resumed until 1951. Compiled
officially by the American League for every season since
1920 except 1927. Available for some seasons prior to
1920 from reconstructed sources.

**Complete Games (CG). **Adopted officially by both
leagues in 1920. Available for all seasons in
major-league history from a combination of official and
reconstructed sources.

**Double Plays (DP). **Adopted officially by both
leagues in 1922. Available for all seasons in
major-league history from a combination of official and
reconstructed sources.

**Doubles (2B).**

**Earned Runs (ER). **Adopted officially by the
National League in 1912 and by the American League in
1913. For a few years after official adoption by both
leagues, runs aided by stolen bases, hit batsmen, and
wild pitches were frequently not counted as earned, and
runs aided by a pitcher's own errors were often counted
as earned. The modern scoring rules for designating runs
as earned came into effect in 1917. Available for all
seasons in major-league history from a combination of
official and reconstructed sources.

**Earned-Run Average (ERA). **Calculated as (earned
runs time nine) divided by innings pitched. Adopted
officially by the National League in 1912 and by the
American League in 1913. See Earned Runs.

**Errors (E). **Included wild pitches and hit
batsmen for pitchers and passed balls for catchers until
1888, but changed retroactively to reflect modern scoring
rules.

**Extra Bases (EB). **Calculated as total bases
minus hits.

**Extra-Base Hits (EBH). **Calculated as doubles
plus triples plus home runs.

**Fielding Percentage (Fld). **Calculated as
(putouts plus assists) divided by (assists plus errors
plus putouts). See Evaluating
Fielding.

**Games (G). **Often not credited to a player
entering a game as a pinch runner or defensive
replacement prior to 1912 in the National League and 1907
in the American League, and inconsistently recorded until
1920.

**Games Behind (GB). **Calculated as [(leader's
wins minus team's wins) plus (team's losses minus
leader's losses)] divided by two. Number of games a
team finished behind the division or league leader.

**Games Finished (GF). **Adopted officially by both
leagues in 1920. Number of games finished by a pitcher in
relief. Available for all seasons in major-league history
from a combination of official and reconstructed
sources.

**Games Relieved (GR). **Calculated as games minus
games started.

**Games Started (GS). **Adopted officially by both
leagues in 1920. Available for all seasons in
major-league history from a combination of official and
reconstructed sources.

**Grounded Into Double Play (GDP). **Adopted
officially by the National League in 1933 and by the
American League in 1939. From 1933 to 1938 in the
National League, charged as hit into double play (HDP)
and included all double plays, not just groundballs, hit
into by the batter.

**Hit by Pitch (HB). **Hit batsmen for pitchers.
Adopted officially by the National League in 1917 and by
the American League in 1920. Batters hit by a pitch were
not entitled to first base until 1887 in the National
League and 1884 in the American Association. Charged to a
pitcher as an error until 1889, but changed retroactively
to reflect modern scoring rules. Available for all
seasons in major-league history from a combination of
official and reconstructed sources.

**Hits (H). **Included bases on balls in 1887, but
changed retroactively to reflect modern scoring
rules.

**Hits per Nine Innings Pitched (H/9). **A pitching
statistic. Calculated as (hits times nine) divided by
innings pitched.

**Home Runs (HR). **Prior to 1920, a game-winning
hit was credited with only as many bases as required to
drive in the winning run. Thus, if a ball went over the
outfield fence and drove in the winning run from third
base, it was only counted as a single. Prior to 1931, a
batted ball was judged fair or foul on the basis of its
location at the time it disappeared from the view of the
umpires. Thus, if a ball went over the outfield fence in
fair territory but left the view of the umpires in foul
territory, it was a foul ball and not a home run. Also
prior to 1931, any fair ball that bounced over the fence
or into the stands was a home run.

**Home Runs per Nine Innings Pitched (HR/9). **A
pitching statistic. Calculated as (home runs times nine)
divided by innings pitched.

**Home-Run Percentage (HR%). **A batting statistic.
Calculated as (home runs times 100) divided by
at-bats.

**Innings Pitched (IP). **Usually included
fractions of an inning from 1876 to 1919, but rounded off
to the next highest inning from 1920 to 1982. Fractions
of an inning have been reconstructed on a game-by-game
basis from 1920 to 1982.

**Intentional Bases on Balls (IBB). **Adopted
officially by both leagues in 1955.

**Isolated Power (Iso). **Calculated as (total
bases minus hits) divided by at-bats, or slugging average
minus batting average. A measure of a player's ability to
hit for power beyond the frequency of hits indicated by
his batting average. Created by Branch Rickey and Allan
Roth in the 1950s.

**Losses (L). **After 1920, official scorers in
both leagues were instructed to designate a winning and
losing pitcher in every game. Official rules specifying
the designation of a winning and losing pitcher were
established in both leagues in 1950. Available for all
seasons in major-league history from a combination of
official and reconstructed sources.

**On-Base Percentage (OBP). **Calculated as (hits
plus bases on balls plus hit by pitch) divided by
(at-bats plus bases on balls plus hit by pitch plus
sacrifice flies), but calculated by Total Baseball
without sacrifice flies in the denominator. Hit by pitch
and sacrifice flies are omitted if unavailable. A measure
of a player's ability to reach base not only by hits, but
by bases on balls and hit by pitch, too. Adopted
officially by both leagues in 1984. Created by Branch
Rickey and Allan Roth in the 1950s.

**On-Base Percentage Plus Slugging Average (OPS).
**A measure of a player's ability both to reach base
and to hit for power. For teams, correlates highly with
runs scored.

**Opponents' Batting Average (OAvg). **See Batting
Average.

**Opponents' On-Base Percentage (OOBP). **See
On-Base Percentage.

**Outs Made (OM). **Calculated as at-bats minus
hits plus sacrifice hits plus sacrifice flies plus caught
stealing plus grounded into double play. Sacrifice hits,
sacrifice flies, caught stealing, and grounded into
double play are omitted if unavailable.

**Passed Balls (PB). **Adopted officially by the
National League in the 1880s and by the American League
in 1925. Charged as an error until 1888, but changed
retroactively to reflect modern scoring rules. Available
for all seasons in major-league history from a
combination of official and reconstructed sources.

**Pitchers' Park Factor (PPF). **Can be expressed
as a whole number (100) or as a decimal (1.00). The
extent to which a pitcher's statistics benefited or
suffered from the ballparks in which his team played its
games. Includes not only the differences between his home
park and the road parks in which his team played, but
also an adjustment for the fact that the pitcher did not
have to face his own team's batters. Generally, an
average park factor is 100, a park factor indicating a
hitters' park is greater than 100, and a park factor
indicating a pitchers' park is less than 100. Park
factors are the same as those provided by *Total
Baseball*, and are based on three-year averages. For
more on park factor, refer to the *Total
Baseball* glossary.

**Pitching Runs (PR). **Calculated as (league
earned-run average minus pitcher's earned-run average)
times (innings pitched divided by nine). The number of
earned runs the pitcher prevented or allowed above or
below the league average assuming the same number of
innings pitched. Zero indicates a league-average pitcher,
a positive total indicates an above-average pitcher, and
a negative total indicates a below-average pitcher. In
order to adjust for park factor, calculate as
[(league earned-run average times pitchers' park
factor) minus pitcher's earned-run average] times
(innings pitched divided by nine). Developed by Pete
Palmer. For more on pitching runs, refer to the *Total
Baseball* glossary. See also Evaluating
Pitching.

**Plate Appearances (PA). **Calculated as at-bats
plus bases on balls plus hit by pitch plus sacrifice hits
plus sacrifice flies. Hit by pitch, sacrifice hits, and
sacrifice flies are omitted if unavailable.

**Putouts (PO). **Awarded to a catcher on a
strikeout.

**Range Factor (Rng). **Calculated as (putouts plus
assists) divided by games. The number of successful plays
a fielder makes per game. If innings played are
available, a more accurate calculation is [(putouts
plus assists) times nine] divided by innings played.
See Evaluating Fielding.

**Reached Base (RB). **Calculated as hits plus
bases on balls plus hit by pitch. Hit by pitch are
omitted if unavailable.

**Runs (R).**

**Runs Batted In (RBI). **Adopted officially by
both leagues in 1920. From 1920 to 1939, included a
runner scored even when the batter grounded into a double
play. Available for all seasons in major-league history
from a combination of official and reconstructed
sources.

**Sacrifice Flies (SF). **A flyball that scored a
runner was counted as a sacrifice hit from 1908 to 1925
and in 1939. From 1926 to 1930, a sacrifice hit included
any flyball that advanced a runner regardless of whether
he scored. Flyballs were not counted as sacrifice hits
and were charged as at-bats from 1931 to 1938 and from
1940 to 1953. A flyball that scored a runner was finally
adopted as a separate, official category in 1954.

**Sacrifice Hits (SH). **Recorded since 1889, but
until 1893 included almost any out that advanced a
runner. From 1894 to 1907, included only bunts used to
advance a runner. Included flyballs that allowed a runner
to score from 1908 to 1925 and in 1939. From 1926 to
1930, included any flyball that advanced a runner
regardless of whether he scored. Charged as an at-bat
from 1889 to 1893. Sacrifice hits allowed by pitchers
were adopted officially by the National League in 1913
and by the American League in 1921.

**Saves (Sv). **Adopted officially by both leagues
in 1969. Available for all seasons in major-league
history from a combination of official and reconstructed
sources.

**Secondary Average (Sec). **Calculated as (total
bases minus hits plus bases on balls plus stolen bases)
divided by at-bats. A measure of a player's offensive
ability beyond his batting average, specifically his
ability to hit for power, draw walks, and steal
bases.

**Shutouts (Sh). **Credited to a pitcher of a
complete-game scoreless victory. Adopted officially by
the National League in 1904 and the American League in
1908. Available for all seasons in major-league history
from a combination of official and reconstructed
sources.

**Singles (1B). **Calculated as hits minus (doubles
plus triples plus home runs).

**Slugging Average (Slg). **Calculated as total
bases divided by at-bats. A measure of a player's ability
to hit for power.

**Stolen Base Attempts (SBA). **Calculated as
stolen bases plus caught stealing.

**Stolen Bases (SB). **Recorded since 1886.
Included advancing extra bases on a hit or an out from
1886 to 1897.

**Stolen-Base Percentage (SB%). **Calculated as
stolen bases divided by (stolen bases plus caught
stealing).

**Strikeouts (SO). **Unavailable for batters from
1897 to 1909 in the National League, from 1901 to 1912 in
the American League, from 1882 to 1888 in the American
Association, for 1884 in the Union Association, and for
1914 and 1915 in the Federal League. Several factors have
influenced strikeout totals over the years. In 1887, four
strikes were required for an out. Until 1887, a batter
could specify a strike zone above or below the waist. The
present distance from home plate to the pitching rubber
of 60 feet, six inches, was not established until 1893.
Prior to 1901 in the National League and 1903 in the
American League, foul balls were not counted as
strikes.

**Strikeout Percentage (SO%). **A batting
statistic. Calculated as (strikeouts times 100) divided
by at-bats.

**Strikeouts per Nine Innings Pitched (SO/9). **A
pitching statistic. Calculated as (strikeouts times nine)
divided by innings pitched.

**Successful Chances (SC). **Calculated as assists
plus putouts.

**Total Chances (TC). **Calculated as assists plus
errors plus putouts.

**Triples (3B).**

**Wild Pitches (WP). **Adopted officially by the
National League in 1903 and by the American League in
1908. Charged to a pitcher as an error until 1888, but
changed retroactively to reflect modern scoring rules.
Available for most seasons in major-league history from a
combination of official and reconstructed sources.

**Winning Percentage (Pct). **Calculated as wins
divided by (wins plus losses).

**Wins (W).** After 1920, official scorers in both
leagues were instructed to designate a winning and losing
pitcher in every game. Official rules specifying the
designation of a winning and losing pitcher were
established in both leagues in 1950. Available for all
seasons in major-league history from a combination of
official and reconstructed sources.

**Sources:**

*The Bill James Historical Baseball Abstract, *by
Bill James (Second Edition, 1988).

"A Brief History of the Home Run," *The
Home Run Encyclopedia**, *edited by Bob
McConnell and David Vincent (1996).

"The Evolution of Baseball Statistics" by Neil Munro,
*STATS
All-Time Major League Handbook**, *edited by
Bill James, John Dewan, Neil Munro, and Don Zminda
(1998), and* **STATS
All-Time Baseball Sourcebook**,* edited by
Bill James, John Dewan, Neil Munro, Don Zminda, and Jim
Callis (1998).

Glossary,*
**Total
Baseball**, *edited by John Thorn, Pete
Palmer, Michael Gershman, and David Pietrusza (Sixth
Edition, 1999).

*The Hidden Game of Baseball, *by John Thorn and
Pete Palmer (1984).