The ratio of the firm’s market value to its book value of assets.
We define the firm’s market value as the book value of assets minus the book value of equity plus the market value of equity   (de Andres, 2008)
 
The book value of total assets minus the book value of common equity plus the market value of common equity divided by the book value of total assets (García et al, 2015)
 
which captures the value of future investment opportunities-The ratio of the market value of assets to the replacement cost of assets. Alternatively, Tobin’s Q can be measured as the market value of assets (book value of assets plus market value of equity minus book value of equity) over the book value of assets (Panagiotis et al, 2007)