Control variables were used to test the possibility that an empirically observed relation
between an independent and a dependent variable is spurious. The selection of the
control variables for each dependent variable was based on prior empirical work,
drawing those variables likely to be related to dependent variables. The control for
dependent variables generally included size, market-to-book ratio, leverage, and
liquidity. The proxy of size is estimated using the logarithm of the book value of total
debt plus the market value of equity. Market-to-book is the ratio of the market value of
equity to book value of equity. Leverage is the book-value ratio of total debt to total
assets. Liquidity is the ratio of current assets to current liabilities. By including these
measures as an independent variable in the regression, we can test whether firm
characteristics have significantly effected on firm’s performance.