all of the above are factors like others have mentioned...smaller parks, better athletes, etc. but did anyone see ESPN the other day when they were talking about the HR records...some guy computed the distance of every Ruth at bat his record setting year and it was determined that if he had been playing today he would have hit 84 homers that yr.
Also, there is no major league pitcher that wants to go into the record books as the guy who gave up the record breaking HR, these guys are extremely competitive and would much better like to be known as the guy who shut down someone's try at a record...during Mac's HR record year there were pitchers who comlained about their home fans and teammates who applauded Mac's homeruns
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