We study a nonlinear relationship between corporate investment and Tobin’s q in the cross section of firms. After correcting for nonlinear errors using a repeated measurement of q derived from analysts’ forecasts, we find evidence of varying investment-q sensitivity across firms. The investment-q sensitivity is low for firms with low q. It then becomes more pronounced at intermediate values before weakening at high values of q, resulting in an S-shaped pattern. In the cross section, the true investment-q relation is therefore not strictly linear. Firm investment is predicted to remain similar among firms with low q, suggesting that increases in q do not necessarily lead firms to increase investment significantly.

We study the classical relationship between a firm’s investment and q , for which an unobserved persistent shock is an important factor in the investment decision. In our setting, besides the potential measurement problem of q , controlling for the unobserved shock becomes a new challenge. We develop an estimation method that addresses both econometric issues given timing and information set assumptions. Using 16,256 unique public firms in the United States from 1975 to 2021, we find that q remains a significant factor of investment even after controlling for the unobserved shock and measurement error.