A Twosome Place's 6.4% slide handed Starbucks Korea most of its new card-spending lead

A Twosome Place's lead had been shrinking since July, when it stood at about 7 billion won ^[7]. In September the gap moved 12.5 billion won in Starbucks' favour ^[13]. Starbucks' own growth supplied 5.0 billion won of that swing, and A Twosome Place's decline supplied the other 7.5 billion won, or 60% ^[13].

As a group, the four chains in the data took in less. Their combined estimated card spending fell from 356.5 billion won in August to 349.3 billion won in September, about 2% ^[17]. Starbucks was the only one of the four to grow, and its share of the four-chain total rose from 32.6% to 34.7% ^[18].

Starbucks has recovered on this measure, or rather it has climbed off the bottom of its slump. September's 121.1 billion won is 20.71 billion won, or 20.6%, above June's 100.39 billion won ^[15]. Each monthly gain has been smaller than the one before: about 9.7% in July, 5.4% in August and 4.3% in September ^[16].

The boycott was not the only drag on spending. After the controversy Starbucks Korea put its summer product launch and promotional events on hold ^[10]. It began bringing them back gradually in July ^[11], the same month card spending started rising ^[3]. The card data cannot separate customers ending a boycott from customers responding to new drinks and discounts that had been withheld since May.

Both papers say Mobile Index counts only credit and debit card payments and leaves out Starbucks' own prepaid cards and mobile gift vouchers ^[4][5]. That exclusion can bias the series in either direction. If prepaid-card holders came back faster than customers paying by credit or debit card, the card figures understate the recovery. If they stayed away longer, the figures overstate it.

There are three ways the September lead could go. Starbucks' own growth could hold it. A return by A Twosome Place to its August level could erase it. Or it could matter little, if total sales moved differently from card spending ^[4]. We think the ranking overstates how far Starbucks has come back, because most of the new lead came from a rival's bad month and Starbucks' monthly growth rate has fallen twice in a row ^[13][16]. The case against us is the share figure. Starbucks gained 2.1 points of share while all three rivals shrank ^[18][8], and A Twosome Place's slide alone does not account for that.

If Starbucks grows by more than September's 4.3% in October while A Twosome Place holds flat or rises, we are wrong ^[2].