63% of people buy things they don’t need because of coupons or a sale.

Using a unique administrative level dataset from a large and diverse U.S. financial institution, we test the impact of rewards on credit card spending and debt. Specifically, we study the impact of cash-back rewards on individuals before and during their enrollment in the program. We find that with an average cash-back reward of $25, spending and debt increases by $79 and $191 a month, respectively during the first quarter. Furthermore, we find that cardholders who do not use their card prior to the cash-back program increase their spending and debt more than cardholders with debt prior to the cash-back program. In addition, we find that 11 percent of cardholders that did not use their cards in the previous 3 months prior to the cash-back program spent at least $50 in the first month of the program. Finally, we find heterogeneous responses by demographic and credit constraint characteristics.

Federal Reserve Bank of Chicago

6 sneaky ways coupons and sales actually make you spend more money

Why We Overspend With Credit

Use Discount Marketing To Get Customers to Spend More - Spectrio

Is Cashback Profitable for Credit Card Companies?

https://www.bizjournals.com/bizjournals/how-to/marketing/2017/10/18-ways-to-encourage-customers-to-spend-more-than.html

https://www.consumerreports.org/cro/news/2013/08/how-americans-shop-for-groceries/index.htm

https://www.quora.com/What-psychological-tricks-do-retailers-use-to-get-people-to-spend-more-money?share=1

Are cashback services worth it?