Will a Ball Travel Further on a Artificial Field

Effect OF ARTIFIALTURF VS. GRASS

written by David W. Smith
June 17, 1995

The event of natural grass vs bogus turf on batting performance has been debatedsince the ersatz fabric was outset installed in the Astrodome in 1966. Many differentkinds of arguments accept been advanced, supported by various types of data.

The present analysis is of all the 22,806 games playedfrom 1984 through 1994, roofing over 1.5 meg at bats. The play past play dataused hither came from the Baseball Workshop in Philadelphia, from which anyone canorder them.

The most common argument put forth is that battingaverages are inflated by bogus turf considering the brawl moves so much faster andtherefore ground balls get through the infield more hands. An test of thissimplest exclamation appears in Tabular array 1.

Table i.

Batting average by league and playing surface, 1984-1994.

League	Surface	Games	At Bats	Hits	BA
AL	Grass	8664	590960	154545	0.262
	Turf	3466	237665	62888	0.265
NL	Grass	5474	372243	95367	0.256
	Turf	5202	352519	89421	0.254
Both	Grass	14138	963203	249912	0.259
	Turf	8668	590184	152309	0.258

Several interesting conclusions may exist fatigued fromthis tabular array. Commencement of all the two leagues play very unlike numbers of games onthe ii surfaces. In the AL in that location are 2.50 games on grass for every one on the carpet;in the NL the figure is ane.05.

The AL has an overall higher batting boilerplate of .263to .255. Nevertheless the differential as a office of surface is quite small, with theAL having a three point increment on turf and the NL a perhaps unexpected 2 pointdrop on the artificial surface. The league differences cancel out, leaving a netof .259 in all games on any surface.

The information in tabular array one is actually much too superficial,however, since dissimilar parks differ in many respects other than the playing surface.For instance, all domed stadia accept artificial surfaces and domes take been suggestedas significant factors in offensive statistics. Some other factors that impact battingaverage besides playing surface are: symmetry of the playing field, extent of foulground, height of fences, prevailing wind weather, average temperature, and altitude.

The assay was therefore refined in an attempt tominimize these other effects (the operative discussion is clearly "minimize",since consummate elimination of all effects also playing surface is a very elusiveobjective). The refinement done here is to modify and expand the batting averagecalculation. Batting average may be defined as the number of successes per opportunity,where the successes are condom hits and the opportunities are at bats. These two basicparameters were adjusted in four ways:

ane. Subtract home runs from hits and at bats. Ballshit over the fence presumably are affected very little by the nature of the playingsurface.

2. Subtract strikeouts from at bats. Since strikeoutsare plays in which the brawl is not contacted, the effect of the playing surface canbe safely ignored.

3. Add sacrifice flies to at bats. Sacrifice fliesare currently not included in at bats (for many years they were), although they areessentially regular fly balls that are not hits.

4. Subtract non-cede bunts from hits and at bats.Although there is very likely an effect of the playing surface on the gamble of asuccessful bunt, the primary analysis is concerned with balls put into play on fullswings. Sacrifice bunts are not at bats, but the data used practise identify bunts, sobunt hits and bunt outs that are not sacrifices are removed.

Net Effect:

Adjusted At Bats = At Bats

+ Sacrifice Flies

- Home Runs

- Strikeouts

- Bunt Hits

- Bunt Outs

These adjustments can be summarized simply: all ballsput into play on full swings are considered and simply assurance put into play on fullswings are considered. In this context "in play" means that a fielder couldconceivably brand a play, therefore the exclusion of home runs. The small number ofinside the park abode runs (ten-fifteen per yr) is disregarded. In add-on each typeof striking: single, double, or triple, is considered separately, since in that location are goodreasons to believe that they will exist afflicted differently by the playing surface.

The analysis will be presented in iii phases: 1)all games for the 11 years in amass; ii) all games for private seasons; three)all games for individual teams for each season. Moving to smaller subsets of thedata, such as the performance of individual batters, tremendously increases the statisticalvariability and is more likely to confuse the analysis than to heighten it.

All Games for eleven Seasons

Past making the adjustments described to a higher place and separatingeach hit type, we obtain the information presented in Tabular array 2. For both leagues individuallyand combined the patterns are unmistakable:

the charge per unit of singles goes downwards on turf virtually 3.9% whilethe rates of doubles and triples get sharply upward, thirteen% and 36%, respectively. The combinationof these values into an adapted batting average (labeled "ABA" in thetable) shows a small increase in the AL for games on artificial surface and the reverseeffect for NL contests. These ii results residue each other so the net consequenceis no difference for the Majors overall.

Table 2.

League	Surface	Games	Singles	Doubles	Triples	ABA
AL	Grass	8664	0.228	0.055	0.00652	0.290
	Turf	3466	0.221	0.064	0.00933	0.294
NL	Grass	5474	0.230	0.053	0.00718	0.290
	Turf	5202	0.219	0.060	0.00909	0.288
Both	Grass	14138	0.229	0.054	0.00677	0.290
	Turf	8668	0.220	0.061	0.00919	0.290

All games for individual seasons

The next approach is to examine each league for eachindividual season, giving united states eleven comparisons for each league. Rather than report amassive list of actual rates, table 3 contains a list of the number of times thateach category increased in games on artificial turf out of the xi seasons for thatleague and how many times that category went down in games on turf. For case,in the xi AL seasons, the actual batting average was college on turf 8 times. In theNL the increase occurred in only 4 of the eleven seasons. The individual hitting categoriesare completely consistent in the surface effect they evidence: each league in each seasonhad a college adapted charge per unit of singles on grass and higher adapted rates of doublesand triples on turf. Combining these three into the adjusted batting average givesproportions similar to the actual batting boilerplate changes.

Table 3.

Proportion of increases on bogus turf in ratesof actual batting boilerplate, rates of singles, doubles, triples and adjusted battingaverage for all seasons, 1984-1994.

League	BA	Singles	Doubles	Triples	ABA
AL	8/11	0/11	11/11	eleven/11	nine/11
NL	4/11	0/11	11/eleven	11/11	4/11

Individual team-seasons

The last stage of the expansion is to consider thenumber of times each individual squad had its rates increment on artificial surfacein a given flavour. For the AL there were 154 squad-seasons from 1984-1994 and forthe NL there were 136. These results are presented in table four, which is parallelto table 3 in its system.

Table four.

Proportion of increases on artificial turf in ratesof actual batting average, rates of singles, doubles, triples and adjusted battingaverage for individual teams for all seasons, 1984-1994.

League	BA	Singles	Doubles	Triples	ABA
AL (all teams)	82/154	50/154	115/154	109/154	87/154
NL (all teams)	53/136	30/136	104/136	94/136	52/136

Although the results shown in Table 4 are consistentwith the earlier information, nosotros see that increased variability is introduced whenthe data sets get smaller. 1 determination to exist drawn hither is that the response ofa given squad in a given season may be contrary to the overall trend without seriouslycompromising that larger picture.

Overall conclusions

i. There is no consistent change in the charge per unit of hitsper adjusted at bat due to artificial surface. There is a slight increase in theAL, which is counterbalanced out by a slight decrease in the NL.

2. In that location is a hit change in the distributionof blazon of striking on artificial surface. Singles are consistently lower on the turf,only doubles and triples are dramatically increased.

Explanations

Whatsoever endeavor to offer a mechanism to business relationship for theseresults must directly consider observable player responses to the ii dissimilar surfaces.Permit us render to the initial premise: the ball moves faster on artificial surface.That exclamation seems to be indisputable, non only by observation from the sidelines,but also by listening to the men who play the game. However, the consequences ofthis increased speed of ground balls is less obvious. The offset idea might bethat more assurance will go through because of the greater speed. Notwithstanding, infieldersclearly play several steps deeper on turf than they do on grass. This greater depthis justified even though it ways they have a longer throw to first base becausethe greater speed with which the ball reaches them ways that they have more timeto make the throw. When an infielder plays deeper, his lateral range is significantlyexpanded, allowing him to get to more assurance than would be possible on grass. Furthermore,when infielders play deeper, they are more able to catch bloopers over the infield(so-called "Texas-Leaguers"). I know of no study which charts the positionof the fielders when each ball is put into play, but I am convinced, based on myown anecdotal observations, that the pattern suggested here is true. I have watchedmany games in Philadelphia (turf) and Memorial Stadium in Baltimore (grass), andthe distance between the infielders and outfielders as they await a pitch at thetwo parks is noticeably different, with a much greater gap on the grass field, eventhough the overall park dimensions are similar and the outfielders are playing nocloser to the fence in Baltimore.

If the infielders do change their positions as suggestedhere, is there are any way to examine this data ready for show of information technology? The bulkof this analysis has involved safety hits, which are of course a minority event. Itherefore went through every play of every game and tabulated the number of timesballs were striking to infielders on outs, including errors and fielder's choices whereno ane was retired besides. Furthermore, this tabulation was subdivided into ballshit on the ground and balls fielded in the air, the latter category including popups and line drives.

Finally, since there is a chance that varying amountsof foul ground will have an outcome, foul balls, either caught or dropped for errors,were as well tabulated. The results of this assay are in Tabular array 5. Rates are calculatedby dividing each value by the adjusted at bats with foul balls removed.

Table v.

Rates of foul balls and outs fielded by infielders,separated by ground balls and balls hit in the air.

League	Surface	Foul %	Ground %	Air %	Infield %
AL	Grass	0.032	0.280	0.078	0.359
	Turf	0.033	0.284	0.077	0.361
NL	Grass	0.034	0.288	0.077	0.365
	Turf	0.031	0.286	0.078	0.364
Both	Grass	0.033	0.283	0.077	0.361
	Turf	0.032	0.285	0.077	0.363

These results show clearly that the surface does nothave an effect on the number of balls fielded by infielders, which would announced tobe in contradiction to the claim asserted above. However, it is more probable thatthese numbers show that the fielders take contradistinct their position on the field tomaintain an optimum chance of getting to a ball.

Infielder positioning was posited as an explanationfor the decrease in singles on artificial turf. The extra base hits require a differentanswer. Since the brawl moves so much more than quickly on turf, a ball which gets throughthe infield will accept a much greater take a chance of getting past the outfielders also.Although it is highly anecdotal, I clearly recollect a game in Philadelphia in the late1970s when Larry Bowa, the Philadelphia shortstop, just missed a ground ball to hisleft, sprawling on his face in a futile dive. The ball rolled to the wall in leftcenter and the batter got a triple. It is highly unlikely that such a brawl, evenif had gotten through the infield, would have become a 3 base hit on a grassfield.

Decision

I additional category worthy of a cursory considerationis bunts. All bunts (sacrifices plus bunt hits plus non-sacrifice bunt outs) occurabout 17% more ofttimes on grass fields than on turf. Since a bunt is an intentionalplay on the part of the batter, one must consider that this significant differencein occurrence reflects player perceptions of the difficulty of bunting on turf.

In that location is an expected, although slight, differencein the success of non-sacrifice bunts equally well, with 39.9% of them existence hits on grassvs 36.6% on artificial surfaces. Although bogus surface seems to have but aminor event on batting boilerplate, in that location is a clear result on the pattern of safe hits.I might expect that the increase in doubles and triples on bogus turf wouldoffset the lower rate of singles and lead to overall higher criminal offense on the rug.However, as shown in Tabular array 6, scoring on grass is actually slightly higher (eight.82runs per game for both teams) than on turf (8.62 runs per game for both teams) duringthe past 11 seasons, although the two leagues differ in the direction of the alter.

Table 6.

Runs scored as a function of league and surface.

League	Surface	Games	Runs	Runs/Game
AL	Grass	8664	78629	9.08
	Turf	3466	31590	nine.11
NL	Grass	5474	46053	8.41
	Turf	5202	43081	8.28
Both	Grass	14138	124682	8.82
	Turf	8668	74671	8.62

Note added in April, 1996. The analysis inTable 6 has a methodological error in that abode runs are non excluded. The properadjustment would exist to subtract the number of runs attributed to home runs and so thatthe result of balls hit in play on scoring could be seen more than conspicuously.

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