Incheon's 91.3 billion won cashback fund covers about 65 days at the Chuseok weekend's pace

The 513% measures one payment channel against itself, with the discount off and then on. Cashback stopped in mid-July and came back on Sept. 18 ^[1][13]. So the 4.6 billion won residents put through Incheon e-eum on Sept. 12 and 13 is roughly what the card does with no reward attached, and the 28.2 billion won of the following weekend is what it does at 10% back with Chuseok groceries to buy ^[4][5][6]. That is 6.13 times ^[1]. Whether any of it is spending that would not otherwise have happened is the question the Incheon Institute's report sets out to answer ^[8].

The report gives two answers and they are not interchangeable. Three years of payouts, 493.3 billion won, produced 1.1372 trillion won of new spending inside the city, or 2.31 won per won of cashback ^[8]. The value-added multiplier, which the report calls the core measure economists use for policy efficiency, came to 1.41 ^[9]. That is 61 won of value added for every 100 won of induced in-city spending ^[2]. The same exercise counts 15,690 jobs, which is 31.4 million won of cashback for each one ^[11][3], and a production-inducement effect of 1.4947 trillion won ^[10].

Both ratios use cashback paid as the denominator. The report does not give the cashback rates in force across the three years. If every won of it had gone out at the current 10%, the 493.3 billion won would sit on about 4.93 trillion won of platform volume, and the 1.1372 trillion won of new spending would be 23% of that ^[6]. The rest is money that would have been spent anyway, on another card or in another week.

The 91.3 billion won behind the restart covers about 913 billion won of eligible spending at the headline rate ^[2][4]. The first weekend ran at 14.1 billion won a day. At that pace the fund is gone in about 65 days, around Nov. 22, five weeks before the benefit is due to expire ^[5][7]. It will not run at that pace, because the monthly cap halves to 500,000 won on Oct. 1 and Chuseok happens once ^[6][7].

The payment mix shows who absorbed the two months without cashback. Restaurants and cafes account for 30% of cumulative payments, general retail such as supermarkets 17%, and food shops including traditional markets and butchers 10% ^[12]. More than 80% of payments are at merchants with annual revenue under 3 billion won ^[14], where e-eum was 20% to 30% of revenue, according to the report, before it went to zero in mid-July ^[13].

Excluding the larger stores did what it was meant to. After Incheon stopped paying cashback at merchants above 3 billion won in revenue in September 2023, the small-business shift multiplier went from 0.56 in 2022 to 1.14 in 2024 ^[15].

In my view the 1.41 is the number to fund this program on, and the weekend spike is not evidence for it. The counter-thesis is fair: the multiplier was estimated by the city's own institute on the city's own program with no control city, and the 2.31 cannot separate a resident who spent more from one who moved a supermarket trip off a credit card. October to December will discriminate between them. If volumes hold near the pre-holiday pace with the cap back at 500,000 won, the cashback added demand; if they slide back toward 4.6 billion won a weekend, it moved spending in time, and the July suspension is what that costs ^[5][7][16].