| Variable symbol | Variable name | Variable definitions |

Dependent variable | RD | R & D investment | The natural logarithm of the R & D investment in this period |

Independent variables | ETR | Corporate tax burden | (income tax expense ? deferred income tax expense)/total profit |

Control variables | LASTRD | Last R & D investment | RD lag phase I |

LASTETR | Last corporate tax burden | ETR lag phase I | |

ROE | Profitability | The total profit/total assets | |

SIZE | Company size | The natural logarithm of total assets | |

LEV | Asset-liability ratio | Total debt/total assets | |

SALE | Total profit | Natural logarithm of total profit |