The shift in consumer demand preferences for vehicles was rather sudden, despite the buildup in fuel prices. Seems that $4/gallon caused a sudden shift in consumer preferences compared to $3/gallon.

Factors limiting the speed of change in vehicle supply:

a. Rental fleet turnover: 1-2 years
b. Auto factory retooling time (not pre-planned): ??? (this is time needed for a car company to significantly change the mix of existing models it sells)
c. Automotive design cycle: 5+ years (this is time to design the next generation vehicle, perhaps incorporating a greater emphasis on fuel economy)