| Variable Type | Variable Measure | Variable Sign | Variable Interpretation |
| Dependent variable | Audit fees | LAF | Natural logarithm of audit fee |
| Independent variable | City-level | City L | City L = 1 if audit firm and company in a same city |
| Economic scale | Scale | Total income Percentile Ranking based on regional -level | |
| Cross terms | City L × Scale |
| |
| Control variable | Company size | Size | Natural logarithm of total asset |
| Short-term Liquidity | Cata | Current assets/current liabilities | |
| Liquidity solvency | Quick | Quick assets/current liabilities | |
| Operational capability | LEV | Total liabilities/total assets | |
| Profitability capability | ROI | Pre-tax income/total assets | |
| Growth capacity | Growth | Growth rate of operating income | |
| Lasting capacity | Loss | Loss = 1 if Net profit less than0,or loss = 0 | |
| Audit opinion | Op | Op = 1 if give Standard without reservation, or op = 0 | |
| Regression year | Year | Fixed variable | |
| Regression industry | Industry | Fixed variable |