ently ▁in ▁The ▁General ▁Theory . ▁Given ▁the ▁importance ▁attached ▁to ▁these ▁concerns ▁in ▁Chapter ▁ 4 , ▁this ▁is ▁a ▁serious ▁defect ... ▁ ▁Vari ables ▁in ▁the ▁equations ▁below ▁are ▁defined ▁as ▁follows : ▁ ▁The ▁conversion ▁factor ▁between ▁w age ▁units ▁and ▁real ▁terms ▁is ▁p   /   W   , ▁so ▁C   =   ( p   /   W   ) · c . ▁W   ▁is ▁assumed ▁given ▁but ▁p   ▁is ▁an ▁unknown ▁which ▁needs ▁to ▁be ▁determined . ▁ ▁The ▁prop ens ity ▁to ▁consume / save ▁The ▁prop ens ity ▁to ▁consume ▁is ▁introduced ▁in ▁Chapter ▁ 8 ▁as ▁the ▁desired ▁level ▁of ▁exp end iture ▁on ▁consumption ▁( for ▁an ▁individual ▁or ▁aggreg ated ▁over ▁an ▁economy ) ▁as ▁a ▁function ▁of ▁income . ▁Let ▁us ▁assume ▁that ▁the ▁proportion ▁ λ ▁of ▁income ▁consum ed ▁is ▁a ▁function ▁of ▁real   ▁income , ▁so ▁ ▁c ▁= ▁y   · λ ( y   )      C   =   Y   ·   λ ( Y   /   ( p   /   W   )) ▁Ke yn es ▁assumes ▁that ▁ λ ( y   ) ▁var ies ▁relatively ▁slowly ▁with ▁y , ▁and ▁that ▁p   /   W   ▁moves ▁only ▁within ▁a ▁narrow ▁comp ass , ▁and ▁thus ▁con cludes ▁that ▁changes ▁in ▁p   /   W   ▁have ▁only ▁a ▁weak ▁effect ▁on ▁C , ▁allowing ▁us ▁to ▁adopt ▁the ▁approximation ▁C