We take a share-of-purchase perspective (e.g., Tellis
1988) that recognizes Internet retailer loyalty as a lack of
search across retailers when making a purchase (Srinivasan,
Anderson, and Ponnavolu 2002), consistent with our
model’s premise.17 A given purchase occasion corresponds
to loyal behavior if no other book retailers or price comparison
shopbots are searched before purchase or to switcher
behavior if at least one other book retailer or shopbot is
searched before purchase.18 This results in a retailer’s SLR
measure being the ratio of switcher purchase occasions to
loyal purchase occasions. Consistent with prior studies
(e.g., Danaher 2007; Moe and Fader 2004a; Park and Fader
2004), we take a daily perspective on panelists’ purchase
activity in forming the measures.