"three point foul" and "clear path" rules were both introduced in the 1995–96 season with the effect of increasing the number of free throws, hand-checking (the amount of contact a defender may make with an opposing player) was banned in 1994 and the use of elbows was banned in 1997 (both rules had seen various degrees of limitation by earlier rule changes) although neither was fully implemented until 2004. The 2004 rule changes, which also included calling the defensive 3 second rule ("[...] a defensive player may not station himself in the key area longer than three seconds"—a longstanding rule which had been ignored by referees) had a major effect, opening up the game and allowing a more free-flowing offense; it encouraged aggressive inside attack based plays (to draw fouls), and has increased the number of fouls given when contact is made on players who drive to the basket. Former ABA and NBA Coach Larry Brown is quoted as saying: "The college game is much more physical (than the NBA) [...] I always tease Michael (Jordan), if he played today, he'd average 50." Calculation All calculations begin with what is called unadjusted PER (uPER). The formula is: When multiplied out and refactored, the equation above becomes: Where , , . With tm, the prefix, indicating of team rather than of player; lg, the prefix, indicating of league rather than of player; min for number of minutes played; 3P for number of three-point field goals made; FG for number of field goals made; FT for number of free throws made; VOP for value of possession (but in reference to the league, in this instance); RB for number of rebounds: ORB for offensive, DRB for defensive, TRB for (total) combined, RBP for percentage of offensive or defensive; others being outlined in basketball statistics. Once uPER is calculated, it must be adjusted for team pace and normalized to the league to become PER: This final step takes away the advantage held by players whose teams play a fastbreak style (and therefore have more possessions and more opportunities to do things on offense), and then sets the league average to 15.00. Also note that it is impossible to calculate PER (at least in the conventional manner described above) for NBA seasons prior to 1978, as the league did not keep track of turnovers among other advanced statistics before that year. References External links CREZ