The Proof:
Why XERA challenges anyone to find a more accurate way to evaluate baseball players:
Note the close proximity of the XERA calculations to actual data. 
Compare XERA to any other algorithm for accuracy.
XERA uses the same formulas each year. 
This is the difference.,Check out the graph, on the right, to see how accurately (hitter's) XERA compares to actual ERA.
In the worst-case scenario, in the last 52 major league-seasons, (hitter's) XERA was off by 0.10 from the actual (pitcher's) ERA! 
Results of XERA pitching formula comparisons start below the hitting figures.
The XERA formulas are not modified to accommodate years of extremely good hitting or pitching.
Minor changes are made (every few years) as new statistical information accumulates. This sheet is current.
The black figures (below) represent actual data. The blue figures are XERA calculations. Copyright © 2011, Dwight R. Gill
These figures are calculated 
from hitting statistics
Hitter's stats Actual
Actual Pitcher's Actual Calculated Batting Slugging
Year AB H 2B 3B HR BB SO SB CS HBP IP XER XERA ERA   H/9 IP 2B/9 IP 3B/9 IP HR/9 IP BB/9 IP SO/9 IP  SB/9 IP CS/9 IP ER IP Average Average OBA OPS
1960 84014 21434 3442 658 2128 8384 12815 923 547 488 22209.0 9460 3.83 3.82 0.01 8.69 1.39 0.27 0.86 3.40 5.19 0.37 0.22 9417 22075.3 .255 .388 .324 .712
1961 97032 25066 3975 754 2730 9897 14947 1046 599 573 25452.3 11419 4.04 4.03 0.01 8.86 1.41 0.27 0.97 3.50 5.29 0.37 0.21 11390 25380.3 .258 .399 .328 .727
1962 110688 28521 4313 853 3001 10936 17568 1348 701 709 29004.3 12707 3.94 3.96 0.02 8.85 1.34 0.26 0.93 3.39 5.45 0.42 0.22 12748 28983.3 .258 .393 .326 .719
1963 109814 27043 4098 791 2704 9591 18773 1236 763 714 29098.7 11365 3.52 3.46 0.06 8.36 1.27 0.24 0.84 2.97 5.81 0.38 0.24 11186 29194.7 .246 .372 .309 .681
1964 110464 27669 4270 760 2762 9621 19212 1176 719 694 29130.3 11588 3.58 3.58 0.00 8.55 1.32 0.23 0.85 2.97 5.94 0.36 0.22 11592 29194.3 .250 .378 .313 .690
1965 109739 26952 4199 787 2688 10036 19283 1449 786 720 29172.7 11517 3.55 3.50 0.05 8.31 1.30 0.24 0.83 3.10 5.95 0.45 0.24 11345 29208.3 .246 .372 .311 .683
1966 109467 27207 4120 820 2743 9331 18804 1455 926 682 29042.0 11417 3.54 3.52 0.02 8.43 1.28 0.25 0.85 2.89 5.83 0.45 0.29 11363 29089.0 .249 .376 .310 .686
1967 109205 26464 4082 792 2299 9665 19413 1373 939 751 29180.7 10542 3.25 3.30 0.05 8.16 1.26 0.24 0.71 2.98 5.99 0.42 0.29 10711 29248.7 .242 .357 .306 .664
1968 108622 25710 3869 697 1995 9156 19143 1515 931 778 29236.0 9836 3.03 2.98 0.05 7.91 1.19 0.21 0.61 2.82 5.89 0.47 0.29 9687 29292.7 .237 .340 .299 .639
1969 131287 32581 4840 849 3119 13429 22473 1850 1118 884 34898.0 13786 3.56 3.61 0.05 8.40 1.25 0.22 0.80 3.46 5.80 0.48 0.29 14005 34906.3 .248 .369 .320 .689
1970 132140 33555 5235 927 3429 13727 22374 1908 1078 825 34860.7 14787 3.82 3.89 0.07 8.66 1.35 0.24 0.89 3.54 5.78 0.49 0.28 15051 34863.0 .254 .385 .326 .711
1971 130544 32547 4931 808 2863 12536 20956 1765 1039 821 34768.0 13429 3.48 3.47 0.01 8.43 1.28 0.21 0.74 3.25 5.42 0.46 0.27 13400 34629.3 .249 .365 .317 .682
1972 124828 30434 4652 746 2534 11727 20718 1807 1105 751 33452.0 12222 3.29 3.26 0.03 8.19 1.25 0.20 0.68 3.16 5.57 0.49 0.30 12133 33385.7 .244 .354 .311 .664
1973 132363 34010 5224 790 3102 13100 20358 2034 1213 755 34873.0 14346 3.70 3.75 0.05 8.78 1.35 0.20 0.80 3.38 5.25 0.52 0.31 14518 34845.7 .257 .379 .325 .704
1974 132256 33969 5206 847 2649 12963 19495 2488 1383 774 34945.3 13904 3.58 3.63 0.05 8.75 1.34 0.22 0.68 3.34 5.02 0.64 0.36 14083 34892.7 .257 .369 .324 .693
1975 131473 33863 5443 887 2698 13402 19280 2524 1369 760 34730.0 14234 3.69 3.71 0.02 8.78 1.41 0.23 0.70 3.47 5.00 0.65 0.35 14316 34652.7 .258 .374 .327 .701
1976 131525 33598 5240 966 2235 12391 18745 3054 1543 684 34928.7 13494 3.48 3.51 0.03 8.66 1.35 0.25 0.58 3.19 4.83 0.79 0.40 13637 34829.7 .255 .361 .320 .681
1977 143974 38037 6441 1170 3644 13757 21722 3017 1779 791 37738.3 16801 4.01 4.00 0.01 9.07 1.54 0.28 0.87 3.28 5.18 0.72 0.42 16768 37749.3 .264 .401 .329 .730
1978 141567 36508 6186 1020 2956 13566 20058 3004 1617 772 37500.3 15573 3.74 3.69 0.05 8.76 1.48 0.24 0.71 3.26 4.81 0.72 0.39 15362 37357.3 .258 .379 .323 .702
1979 142792 37911 6415 1066 3433 13601 20035 2983 1598 754 37478.0 16677 4.00 4.00 0.00 9.10 1.54 0.26 0.82 3.27 4.81 0.72 0.38 16669 37309.3 .265 .397 .330 .727
1980 144160 38144 6345 1076 3087 13190 20212 3294 1610 657 37861.0 16260 3.87 3.84 0.03 9.07 1.51 0.26 0.73 3.14 4.80 0.78 0.38 16162 37708.3 .265 .388 .326 .714
1981 94467 24157 4000 659 1781 8868 13237 2021 1100 464 25095.3 9962 3.57 3.58 0.01 8.66 1.43 0.24 0.64 3.18 4.75 0.72 0.39 9992 25004.3 .256 .369 .320 .689
1982 144149 37651 6316 964 3379 13302 21221 3176 1617 677 37878.3 16354 3.89 3.86 0.03 8.95 1.50 0.23 0.80 3.16 5.04 0.75 0.38 16258 37869.7 .261 .389 .324 .713
1983 143538 37443 6463 1033 3301 13518 21716 3325 1619 717 37742.0 16405 3.91 3.87 0.04 8.93 1.54 0.25 0.79 3.22 5.18 0.79 0.39 16241 37728.7 .261 .389 .325 .714
1984 143829 37381 6213 985 3258 13320 22500 3032 1511 668 37704.7 15961 3.81 3.81 0.00 8.92 1.48 0.24 0.78 3.18 5.37 0.72 0.36 15965 37804.3 .260 .385 .323 .708
1985 143075 36778 6423 965 3602 13838 22451 3097 1431 699 37658.7 16667 3.98 3.89 0.09 8.79 1.54 0.23 0.86 3.31 5.37 0.74 0.34 16292 37710.3 .257 .391 .323 .714
1986 143106 36880 6511 855 3813 14227 24706 3312 1620 812 37674.3 16795 4.01 3.97 0.04 8.81 1.56 0.20 0.91 3.40 5.90 0.79 0.39 16629 37765.7 .258 .395 .326 .721
1987 144095 37895 6793 896 4458 14389 25099 3585 1529 842 37574.7 18338 4.39 4.29 0.10 9.08 1.63 0.21 1.07 3.45 6.01 0.86 0.37 17925 37734.3 .263 .415 .331 .747
1988 142568 36244 6386 840 3180 12984 23355 3300 1418 918 37667.7 15791 3.77 3.73 0.04 8.66 1.53 0.20 0.76 3.10 5.58 0.79 0.34 15626 37706.3 .254 .378 .318 .696
1989 142821 36293 6307 868 3083 13528 23650 3116 1441 801 37715.0 15543 3.71 3.71 0.00 8.66 1.51 0.21 0.74 3.23 5.64 0.74 0.34 15551 37786.7 .254 .375 .320 .695
1990 142768 36817 6526 865 3317 13852 23853 3290 1510 861 37563.7 16185 3.88 3.86 0.02 8.82 1.56 0.21 0.79 3.32 5.72 0.79 0.36 16116 37624.7 .258 .385 .325 .710
1991 142967 36558 6499 894 3383 13984 24390 3120 1567 905 37769.7 16055 3.83 3.91 0.08 8.71 1.55 0.21 0.81 3.33 5.81 0.74 0.37 16410 37801.7 .256 .385 .323 .708
1992 142895 36544 6563 845 3038 13682 23538 3264 1601 980 37829.7 15659 3.73 3.75 0.02 8.69 1.56 0.20 0.72 3.26 5.60 0.78 0.38 15744 37795.7 .256 .377 .322 .700
1993 154995 41088 7449 940 4030 15110 26310 3263 1660 1200 40507.0 18387 4.09 4.19 0.10 9.13 1.66 0.21 0.90 3.36 5.85 0.72 0.37 18861 40487.7 .265 .403 .332 .736
1994 110266 29743 5723 702 3306 11131 19766 2258 1032 876 28586.3 14105 4.44 4.51 0.07 9.36 1.80 0.22 1.04 3.50 6.22 0.71 0.32 14330 28573.3 .270 .424 .339 .763
1995 138571 36975 6958 824 4081 14240 25425 2933 1257 1219 36032.0 17496 4.37 4.45 0.08 9.24 1.74 0.21 1.02 3.56 6.35 0.73 0.31 17822 36024.0 .267 .417 .338 .755
1996 156801 42320 7987 855 4962 16093 29308 3239 1343 1404 40560.7 20365 4.52 4.61 0.09 9.39 1.77 0.19 1.10 3.57 6.50 0.72 0.30 20780 40572.3 .270 .427 .340 .767
1997 155438 41471 8004 883 4640 15666 29937 3308 1564 1449 40454.0 19475 4.33 4.39 0.06 9.23 1.78 0.20 1.03 3.49 6.66 0.74 0.35 19730 40474.3 .267 .419 .337 .756
1998 167116 44489 8741 899 5064 16447 31893 3284 1505 1587 43434.7 21019 4.36 4.43 0.07 9.22 1.81 0.19 1.05 3.41 6.61 0.68 0.31 21387 43474.0 .266 .420 .335 .755
1999 167205 45339 8744 931 5530 17901 31134 3421 1519 1579 43210.0 22290 4.64 4.71 0.07 9.44 1.82 0.19 1.15 3.73 6.48 0.71 0.32 22606 43231.0 .271 .434 .345 .778
2000 167290 45246 8902 952 5693 18238 31356 2923 1323 1572 43244.3 22500 4.68 4.77 0.09 9.42 1.85 0.20 1.18 3.80 6.53 0.61 0.28 22918 43209.7 .270 .437 .345 .782
2001 166234 43879 8813 928 5458 15806 32404 3103 1408 1890 43287.3 21397 4.45 4.42 0.03 9.12 1.83 0.19 1.13 3.29 6.74 0.65 0.29 21247 43331.3 .264 .427 .332 .759
2002 165582 43272 8700 921 5059 16246 31394 2750 1282 1746 43269.0 20690 4.30 4.28 0.02 9.00 1.81 0.19 1.05 3.38 6.53 0.57 0.27 20570 43254.3 .261 .417 .331 .748
2003 166737 44057 8827 934 5207 15889 30801 2573 1132 1849 43335.0 21158 4.39 4.40 0.01 9.15 1.83 0.19 1.08 3.30 6.40 0.53 0.24 21186 43331.3 .264 .422 .333 .755
2004 167353 44522 8919 898 5451 16222 31828 2589 1100 1850 43394.0 21616 4.48 4.46 0.02 9.23 1.85 0.19 1.13 3.36 6.60 0.54 0.23 21527 43377.0 .266 .428 .335 .763
2005 166335 43991 8863 888 5017 15207 30644 2566 1069 1797 43232.3 20795 4.33 4.29 0.04 9.16 1.85 0.18 1.04 3.17 6.38 0.53 0.22 20612 43188.7 .264 .419 .330 .749
2006 167341 45073 9135 952 5386 15847 31655 2767 1110 1817 43258.0 21810 4.54 4.53 0.01 9.38 1.90 0.20 1.12 3.30 6.59 0.58 0.23 21758 43195.7 .269 .432 .337 .768
2007 167776 44974 9198 937 4957 16078 32189 2917 1000 1755 43411.0 21355 4.43 4.47 0.04 9.32 1.91 0.19 1.03 3.33 6.67 0.60 0.21 21574 43332.3 .268 .423 .336 .758
2008 166714 43972 9014 886 4878 16337 32884 2799 1035 1672 43357.7 20788 4.32 4.32 0.00 9.13 1.87 0.18 1.01 3.39 6.83 0.58 0.21 20830 43311.3 .264 .416 .333 .749
2009 165849 43524 8737 949 5042 16620 33591 2970 1133 1590 43272.0 20830 4.33 4.32 0.01 9.05 1.82 0.20 1.05 3.46 6.99 0.62 0.24 20779 43201.7 .262 .418 .333 .751
2010 165352 42554 8486 866 4613 15778 34305 2959 1128 1549 43304.7 19615 4.08 4.08 0.00 8.84 1.76 0.18 0.96 3.28 7.13 0.61 0.23 19629 43347.7 .257 .403 .325 .728
2011 165705 42267 8399 898 4552 15018 34488 3279 1261 1554 43618.7 19381 4.00 3.94 0.06 8.72 1.73 0.19 0.94 3.10 7.12 0.68 0.26 19067 43618.7 .255 .399 .321 .720
  7286892 1890620 337125 45776 191318 703372 1257412 134788 65188 54636 1912110.3 850150 4.00 4.01 0.01 8.90 1.59 0.22 0.90 3.31 5.92 0.63 0.31 851505 1911664.7 .260 .397 .327 .724
The hitting figures generated from pitching statistics are just as impressive:
. . . and how well the pitching stats "estimated" hitter's stats . . .
This is a year-by-year rundown, for the same timeframe, of MLB pitching stats.   Batting Averages . . . 
The green figures represent actual pitching stats.
The blue figures are XERA formulations for AB, batting average, slugging average, on base average, and OPS.
The black figures represent the actual data compiled by hitters in the corresponding seasons.
 Est.   Actual   Est Slg   Actual Slg   Est.   Actual   Est.   Actual  Est Actual ABS Est.
Year IP ER H BB  SO   HR  HBP  AB   Avg   Avg   Avg   Avg   OBA   OBA   OPS   OPS  ERA ERA dif. ER
1960 22209.0 9417 21434 8384 12817 2128 488 83971 .255 .255 .389 .388 .326 .324 .716 .712 3.93 3.82 0.11 9695
1961 25452.3 11390 25066 9897 14952 2730 573 96719 .259 .258 .404 .399 .332 .328 .736 .727 4.18 4.03 0.15 11818
1962 29004.3 12748 28521 10936 17567 3001 709 110235 .259 .258 .400 .393 .330 .326 .730 .719 4.09 3.96 0.13 13175
1963 29098.7 11186 27043 9591 18773 2704 714 109265 .247 .246 .378 .372 .312 .309 .691 .681 3.71 3.46 0.25 11994
1964 29130.3 11592 27669 9621 19212 2762 694 109983 .252 .250 .384 .378 .316 .313 .700 .690 3.78 3.58 0.20 12232
1965 29172.7 11345 26952 10036 19283 2688 720 109416 .246 .246 .376 .372 .314 .311 .690 .683 3.69 3.50 0.19 11973
1966 29042.0 11363 27207 9331 18805 2743 682 109273 .249 .249 .381 .376 .312 .310 .693 .686 3.74 3.52 0.22 12067
1967 29180.7 10711 26464 9665 19413 2299 751 109004 .243 .242 .360 .357 .309 .306 .669 .664 3.41 3.30 0.10 11051
1968 29236.0 9687 25710 9156 19143 1995 778 108445 .237 .237 .344 .340 .301 .299 .645 .639 3.15 2.98 0.17 10234
1969 34898.0 14005 32581 13429 22473 3119 882 131101 .249 .248 .376 .369 .322 .320 .699 .689 3.73 3.61 0.11 14450
1970 34860.7 15051 33555 13727 22374 3429 825 131895 .254 .254 .391 .385 .328 .326 .719 .711 3.96 3.89 0.07 15320
1971 34768.0 13400 32547 12536 20956 2863 821 130605 .249 .249 .370 .365 .319 .317 .689 .682 3.60 3.47 0.13 13907
1972 33452.0 12133 30434 11727 20718 2534 751 124891 .244 .244 .358 .354 .312 .311 .670 .664 3.41 3.26 0.14 12660
1973 34873.0 14518 34010 13100 20358 3102 755 132210 .257 .257 .385 .379 .328 .325 .713 .704 3.83 3.75 0.08 14822
1974 34945.3 14083 33969 12963 19495 2649 774 132307 .257 .257 .373 .369 .327 .324 .699 .693 3.60 3.63 0.03 13972
1975 34730.0 14316 33863 13402 19280 2698 761 131560 .257 .258 .375 .374 .330 .327 .705 .701 3.66 3.71 0.05 14112
1976 34928.7 13637 33598 12391 18745 2235 684 131867 .255 .255 .360 .361 .322 .320 .682 .681 3.36 3.51 0.15 13039
1977 37738.3 16768 38037 13757 21722 3644 791 144227 .264 .264 .399 .401 .331 .329 .730 .730 4.02 4.00 0.02 16846
1978 37500.3 15362 36508 13566 20058 2956 772 141971 .257 .258 .376 .379 .325 .323 .701 .702 3.65 3.69 0.03 15222
1979 37478.0 16669 37911 13601 20035 3433 754 143230 .265 .265 .396 .397 .332 .330 .727 .727 3.96 4.00 0.04 16482
1980 37861.0 16162 38144 13190 20212 3087 657 144567 .264 .265 .386 .388 .328 .326 .714 .714 3.75 3.84 0.09 15791
1981 25095.3 9992 24157 8868 13237 1781 464 94741 .255 .256 .366 .369 .322 .320 .688 .689 3.48 3.58 0.10 9716
1982 37878.3 16258 37651 13302 21221 3379 677 144234 .261 .261 .390 .389 .326 .324 .716 .713 3.85 3.86 0.02 16195 Slugging and OBA . . . 
1983 37742.0 16241 37443 13518 21716 3301 717 143685 .261 .261 .387 .389 .327 .325 .715 .714 3.82 3.87 0.06 16000
1984 37704.7 15965 37381 13320 22500 3258 668 143597 .260 .260 .386 .385 .326 .323 .712 .708 3.78 3.81 0.03 15822
1985 37658.7 16292 36778 13838 22451 3602 699 142872 .257 .257 .391 .391 .326 .323 .717 .714 3.92 3.89 0.03 16419
1986 37674.3 16629 36880 14227 24706 3813 812 143193 .258 .258 .397 .395 .328 .326 .725 .721 4.01 3.97 0.04 16786
1987 37574.7 17925 37895 14389 25099 4458 842 143896 .263 .263 .419 .415 .334 .331 .752 .747 4.38 4.29 0.08 18277
1988 37667.7 15626 36244 12984 23355 3180 918 142506 .254 .254 .378 .378 .321 .318 .698 .696 3.66 3.73 0.07 15337
1989 37715.0 15551 36293 13528 23650 3083 801 142690 .254 .254 .375 .375 .322 .320 .698 .695 3.63 3.71 0.08 15203
1990 37563.7 16116 36817 13852 23853 3317 861 142761 .258 .258 .385 .385 .327 .325 .712 .710 3.79 3.86 0.07 15820
1991 37769.7 16410 36558 13984 24390 3383 905 143141 .255 .256 .384 .385 .326 .323 .709 .708 3.78 3.91 0.13 15878
1992 37829.7 15744 36544 13682 23538 3038 980 143236 .255 .256 .375 .377 .324 .322 .699 .700 3.62 3.75 0.12 15228
1993 40507.0 18861 41088 15110 26310 4030 1200 155300 .265 .265 .402 .403 .334 .332 .737 .736 4.06 4.19 0.13 18292
1994 28586.3 14330 29743 11131 19766 3306 876 110388 .269 .270 .422 .424 .341 .339 .763 .763 4.40 4.51 0.11 13976
1995 36032.0 17822 36975 14240 25425 4081 1219 138689 .267 .267 .417 .417 .340 .338 .757 .755 4.33 4.45 0.12 17341
1996 40560.7 20780 42320 16093 29308 4962 1404 156836 .270 .270 .429 .427 .343 .340 .772 .767 4.52 4.61 0.09 20370
1997 40454.0 19730 41471 15666 29937 4640 1449 155804 .266 .267 .418 .419 .339 .337 .757 .756 4.33 4.39 0.06 19457
1998 43434.7 21387 44489 16447 31893 5064 1583 167241 .266 .266 .419 .420 .337 .335 .757 .755 4.35 4.43 0.08 21007
1999 43210.0 22606 45327 17891 31119 5528 1578 167271 .271 .271 .435 .434 .347 .345 .782 .778 4.65 4.71 0.05 22345
2000 43244.3 22918 45246 18238 31356 5693 1572 167299 .270 .270 .438 .437 .348 .345 .785 .782 4.72 4.77 0.05 22676
2001 43287.3 21247 43879 15806 32404 5458 1890 166318 .264 .264 .426 .427 .335 .332 .760 .759 4.48 4.42 0.06 21546
2002 43269.0 20570 43272 16246 31394 5059 1746 165587 .261 .261 .415 .417 .334 .331 .748 .748 4.31 4.28 0.03 20730
2003 43335.0 21186 44057 15889 30801 5207 1849 166478 .265 .264 .421 .422 .335 .333 .757 .755 4.40 4.40 0.00 21204
2004 43394.0 21527 44522 16222 31828 5451 1850 167161 .266 .266 .428 .428 .338 .335 .766 .763 4.52 4.46 0.05 21771
2005 43232.3 20612 43991 15207 30644 5017 1797 166139 .265 .264 .418 .419 .333 .330 .751 .749 4.32 4.29 0.02 20731
2006 43258.0 21758 45073 15847 31655 5386 1817 167296 .269 .269 .430 .432 .339 .337 .769 .768 4.52 4.53 0.01 21733
2007 43411.0 21574 44962 16073 32180 4956 1754 167661 .268 .268 .419 .423 .339 .336 .758 .768 4.33 4.47 0.15 20868
2008 43357.7 20830 43972 16337 32884 4878 1672 166625 .264 .264 .413 .416 .336 .333 .749 .749 4.25 4.32 0.07 20463
2009 43272.0 20779 43524 16620 33591 5042 1590 166009 .262 .262 .415 .418 .335 .333 .750 .751 4.30 4.32 0.02 20658
2010 43306.2 19629 42553 15778 34302 4613 1548 165285 .257 .257 .401 .403 .328 .325 .729 .728 4.04 4.08 0.04 19435
2011 43527.3 19067 42267 15018 34488 4552 1554 165688 .255 .255 .397 .399 .323 .321 .719 .720 3.96 3.94 0.02 19135
Totals 1912111.9 851505 1890595 703357 1257392 191315 54628 7286366 .259 .260 .398 .397 .329 .327 .727 .724 4.01 4.01 0.00 851281
. . . and OPS . . .