REGULARITY, RECENCY AND RATES

Survey researchers often use the recency question format - ''When was the last time you...'' - to estimate purchase or usage rates. This for mat is particularly useful when the behavior in question is of a sensi tive nature. The calculation of interpurchase times and, in turn, rate s from recency format responses requires an a priori assessment of the distribution of interpurchase times. Although the usual assumption is that interpurchase times are exponential, evidence indicates that tim es between purchases are more regular. We relax the exponential assump tion and measure the effects of more regular purchase behavior, discre te purchase behavior and the dead period between purchases on estimate d rates. Even though our focus is on recency, our results also give so me insights into the commonly reported frequency based result that sho ws heavy consumers are 'more regular' in their purchasing behavior.