The Discount rate is one of the important variables in the inter-temporal analysis which makes it possible to compare the current and the future values and enables economic agents and policymakers to make better decisions. In this context, the discount rate is a vital variable for the accurate evaluation of economic projects. Considering the different approaches that governmental and private sectors use to implement the investment projects, for evaluation of the governmental and public projects, a separate discount rate is used called social discount rate (SDR). In this article by using the structural equation modeling, we have estimated the SDR trend in the Iranian economy during the period 1996- 2016. To do that by extracting influencing & consequence factors of SDR (as a latent variable), we applied a Multiple Indicators and Multiple Causes (MIMIC) model. The SDR trend, as the main finding of this paper, seems to be robust enough due to its explanatory power for fluctuations of the Iranian economy in reality. The results imply that the SDR has had a mild decreasing trend in Iran's economy during the sample period and among influencing variables, the inflation rate has had the most impact on its trend. Accordingly, when the level of prices rocketed during the periods 2012-14, the SDR trend experienced a more than 60% increasing jump. However, the GDP has been the variable that mostly affected by the SDR fluctuations. It seems that controlling inflation and consequently social inflationary expectation can be proposed as a proper policy recommendation to manage SDR and its distorting impacts in Iran.