▁At ▁other ▁times , ▁though , ▁tar iff ▁re venue ▁was ▁considered ▁more ▁important ▁than ▁free ▁intellectual ▁property . ▁ ▁During ▁World ▁War ▁II , ▁neutral ▁Switzerland ▁became ▁the ▁primary ▁tra ff icker ▁of ▁art ▁on ▁the ▁European ▁continent . ▁ ▁Most ▁" de generate " ▁works ▁of ▁art ▁that ▁the ▁Naz i ▁government ▁p urg ed ▁from ▁German ▁museum s ▁were ▁sold ▁there , ▁where ▁they ▁largely ▁entered ▁black ▁mark ets . ▁ ▁Since ▁the ▁war ▁ended , ▁there ▁has ▁been ▁a ▁massive , ▁on going ▁effort ▁to ▁recover ▁all ▁of ▁these ▁works . ▁ ▁For ▁fifteen ▁years ▁following ▁the ▁war , ▁ 4 5 , 0 0 0 ▁pieces ▁were ▁returned ▁to ▁France , ▁mostly ▁to ▁Jewish ▁own ers . ▁ ▁Today , ▁almost ▁every ▁country ▁in ▁the ▁world ▁has ▁restrictions ▁and ▁reg ulations ▁on ▁the ▁export ▁of ▁cultural ▁property . ▁ ▁Currently , ▁most ▁art ▁au ctions ▁are ▁facil itated ▁on ▁online ▁sites ▁such ▁as ▁e B ay ▁and ▁Laur itz . com . ▁ ▁Econom ic ▁theory ▁of ▁art ▁trade ▁ ▁Fine ▁art ▁proves ▁complicated ▁for ▁econom ists ▁to ▁analyze , ▁mostly ▁because ▁trade ▁in ▁unique ▁art ▁is ▁in ▁large ▁part ▁trade ▁between ▁consum ers ▁– ▁the ▁" second ary ▁market " ▁– ▁rather ▁than ▁the ▁" primary ▁market " ▁trade ▁between ▁the ▁producer ▁( art ist ) ▁and ▁the ▁consumer . ▁ ▁For ▁example , ▁when ▁a ▁museum ▁bu ys ▁a ▁sculpt ure ▁from ▁a ▁private ▁collect or , ▁the ▁exchange ▁is ▁between ▁two ▁consum ers ▁and ▁considered