Hastily scribbled answer for Econs

Luxury - inelastic
Higher income/willingness to switch due to high prestige

Necessity
Income increase - limited capacity to use

Inferior
Income increase - usage decrease

PED.
price discrimination, product differentiation, advertistment,
BUT increase cost

YED
economic downturn
-lux
-inf

end: limitaions of elasticity.
ceteris paribus
not accurate - taste & expectations are not quantifiable

ss rise, dd fall - reinforce

ss fall, dd rise - reinforce

ss rise, dd rise -indeterminate
ss increase cannot catch up with rise in dd,
short run, rise in dd outweighs the increase in ss.

Marker's comments:

"Spaghetti is not a luxury good!"

"Don't tell me that maggie(noodles) is inelastic where spaghetti is elastic. Huh? I mean.. If you had said rubber band..."