| Type | Index | Variable name | Variable definition and calculation method |
| dependent variable | Purpose of M & A | Target | Dummy variable. The value is 1 if the sample is the real M & A target, otherwise the value is 0. |
| independent variable | interlocking directorates | NumInterlock | The number of interlocking directorates at the end of the previous year of the first announcement day |
| control variables
| company size | Size | Relative total assets scale. The total assets of target divided by total assets of the acquiring company at the end of the previous year of first announcement day |
| Boardsize | Numdir | The board size of target company at the end of the previous year of the first announcement day | |
| investment value | Q | The Tobin’s Q ratio of target company at the end of the previous year of the first announcement day (excluded) | |
| PE | PE ratio of target company at the end of the previous year of the first announcement day | ||
| Profitability | ROE | Return on equity of target company at the end of the previous year of the first announcement day | |
| Growth | MRGR | Main business revenue growth rate of target company at the end of the previous year of the first announcement day | |
| Leverage ratio | DER | Debt equity ratio of target company at the end of the previous year of the first announcement day | |
| ownership structure | Top1 | The proportion of the largest shareholder of target company at the end of the previous year of the first announcement day | |
| Top10 | The proportion of the top ten shareholders of target company at the end of the previous year of the first announcement day | ||
| Stock Volatility | Beta | Beta value of target company during the previous year of the first announcement day | |
| Year | Year | The year of the first announcement |