How many coupons in a deal does a consumer actually buy?

I try to answer this question by studying 206,990 transactions of 1,395 deals which are sold on a Vietnam group-buying site in 12 months. There are about 290 deals, each of which has sold over 500 coupons. A transaction, in this context, records the total number of coupons which a consumer bought in a deal. For example, if Mr. A bought coupons of a deal at different dates (e.g., 5 coupons on

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