| variable |
| Variable definitions |
| Revenue and Costs | Rev | Operating revenue for the current year |
| Cost | Total operating costs: Current operating costs + Taxes and Surcharges + Selling and administrative expenses | |
| lnRev | Ln (Current year’s revenue/last year’s revenue) | |
| lnCost | Ln (Current year’s total operating costs/last year’s total operating costs) | |
| D | Dummy variable, if the operating income of the current year is lower than that of the previous year, it will be 1, otherwise it will be 0 | |
| Supplier relationship (Supply) | SP | Supplier association degree: Total purchase amount of the top five suppliers from associated suppliers/total annual purchase amount (association includes associates, joint ventures and subsidiaries) |
| SPSC | Influence of associated suppliers: association degree * concentration degree | |
| SC | Supplier concentration degree: Total purchase amount from the top five suppliers/total purchase amount | |
| SS | Supplier volatility degree: Standard deviation/mean of supplier concentration degree in previous three years | |
| Control variables | AI | Total assets/revenue |
| EI | Total number of employees/operating revenue (unit is ten thousand) | |
| Dec | Dummy variable, if the operating income declines for two consecutive years, the value is 1; otherwise, it is 0 | |
| Inde | Number of independent directors/number of all directors | |
| Year | Annual dummy variable |