A group of workplace efficiency analysts conducted a survey at company Y and discovered that 90% of its staff experienced a 'post-lunch dip' between the hours of 1:00 pm and 3:00 pm. During this period, each employee's productivity decreased by an average of 25%. The analysts recommended that management allow employees to take their lunch breaks between 1:00 pm and 3:00 pm, as employees do not need to be productive while eating. The analysts' conclusion relies on which of the following assumptions?