This work estimates the relationship between the economic expectations given by Tobin's q variables, terms of exchange and 3-month economic expectations with private gross investment for the period from the first quarter of 2010 to the first quarter of 2020, under the stress scenario of the COVID-19 pandemic. Through an econometric model, results were obtained such as that the variation in private gross investment VIBP has an inertial behavior with a coefficient of 0.258791, shadow cost of capital or q of Tobin QTC with a coefficient of -0.03213, as well as terms of TI exchange with a coefficient of 0.805618. This indicates that the private investment decision by the companies analyzed depends on factors such as economic expectations, the inertial effect of investment and the shadow cost of capital expressed in Tobin's q.

In this paper, we perform an empirical study to investigate the impact of economical stability on the amount of investment coming from the private sector. We calculate macroeconomics instability index (MII) using the existing methods in the literature. We have also used Glezakos (1973) method [Glezakos,C.(1973). Export instability and economic growth: A statistical verification. Economic Development and Cultural Change, 21(3), 670-678.], which considers long-term deviation of real values as instability index. Therefore, we use four variables of inflation rate (TINF), the ratio of budget deficit on growth domestic product (GDP) (TBD), foreign debt on GDP (TFD) and the ratio of actual currency rate on nominate currency (TRO). The preliminary results show that the short-term changes on logarithm of investment from private sector (LNIP) with one lag and logarithm of value added (LNIV) have positive impact on LNIP. In addition, any short term changes on logarithm of MII (LNMII) has negative and meaningful impact on LNIP and approximately 0.67 percent of difference between the actual and long term are discounted in each period. The results indicate that instability index has negative effect even in short term on Iran & apos; s industry. This shows the relevant importance of instability on economy.