Unseasonal weather led to unanticipated damage and maintenance at oil refineries that produce diesel fuel for boats, leading to a sharp shortage in supply. This caused the price of diesel fuel to increase from $3 per gallon to $5 per gallon. However, the quantity bought by people did not decrease significantly. In this case, demand for diesel fuel is
. The study of demand was done using
that involved computing volumes sold at different locations at the same time.