The key independent variable was the indicator
of end-of-aisle display, with the number of display locations,
price per volume, proportion of the week on price promotion,
average price of other products in the same category, total number
of trolleys purchasing any product from the category in the week,
and indicators of each week (which capture seasonal variations in
the demand for particular items) as control variables. It should be
noted that displaying an item on an aisle end entails additional
shelf space (as products are still displayed on the main shelves as
well). This component of end-of-aisle display is captured by the
variable comprising the number of display locations allocated to
each item.