Marketing claims our card-linked merchant offers program is a big win: the 500,000 enrolled customers spent $12,000 each this year versus $9,200 for non-enrolled, so the program drove $1.4 billion in incremental spend. But enrolled customers were already spending $11,000 the year before they joined, and non-enrolled spent $8,800 last year. How would you evaluate this claim, and what's the real lift?

营销团队说商户返利计划很成功：报名的50万客户今年人均消费1.2万美元，没报名的只有9200美元，所以计划带来了14亿美元增量消费。但报名的人报名前一年人均就有1.1万，没报名的去年是8800。你怎么评估这个结论？真实增量大概有多少？