▁quickly , ▁at ▁a ▁compet itive ▁market - price ▁which ▁is ▁below ▁the ▁soci ally ▁established ▁normal ▁valu ation ▁for ▁that ▁kind ▁of ▁product ▁which ▁applies ▁in ▁market - tra de , ▁princip ally ▁by ▁means ▁of ▁a ▁better ▁labour - exp lo itation ▁rate ▁and ▁higher ▁product ivity ▁than ▁their ▁compet itors , ▁which ▁low ers ▁the ▁cost - price ▁per ▁unit ▁of ▁product ▁in ▁the ▁total ▁turn over , ▁yet ▁provides ▁a ▁superior ▁profit ▁rate ▁on ▁capital ▁inv ested , ▁even ▁if ▁the ▁s elling ▁price ▁is ▁below ▁the ▁normal ▁valu ation . ▁ ▁Such ▁price - cut ting ▁competition ▁is ▁limited ▁in ▁scope ▁however , ▁because ▁if ▁compet itors ▁adopt ▁the ▁same ▁production ▁methods , ▁the ▁product ivity ▁advantage ▁will ▁disappear . ▁In ▁addition , ▁beyond ▁a ▁certain ▁point ▁workers ▁will ▁begin ▁to ▁resist ▁their ▁explo itation , ▁and ▁they ▁may ▁join ▁trade ▁un ions . ▁And , ▁if ▁market ▁prices ▁for ▁products ▁were ▁reduced ▁to ▁their ▁most ▁compet itive ▁cost - pr ices ▁only , ▁prof its ▁would ▁fall ▁to ▁zero . ▁This ▁leads ▁to ▁constant ▁attempts ▁world wide ▁to ▁improve ▁production ▁techniques ▁to ▁cut ▁costs , ▁improve ▁product ivity ▁and ▁hold ▁down ▁labour - cost s , ▁but ▁ultimately ▁also ▁to ▁a ▁decl ine ▁in ▁the ▁labor - content ▁of ▁comm od ities . ▁Therefore , ▁their ▁values ▁will ▁also ▁decl ine ▁over ▁time ; ▁more ▁and ▁more ▁comm od ities ▁are ▁produced , ▁for ▁a ▁larger ▁and ▁larger ▁market , ▁at ▁an ▁increasing ly ▁che aper ▁cost