Establishing economic justice, including improving income distribution, is one of the most important goals in society. This becomes important when the impact of factors affecting income inequality in society can be examined by careful modeling. The main purpose of this study is to investigate the effect of macroeconomic uncertainty and foreign trade on income distribution among income deciles. For this purpose, a system based on fuzzy rules in the form of numbers - Z (Z -FRBS) has been used to calculate the upper, middle and lower limits along with the degree of validity of predicting the limits of each income decile during the period 1375-1397. The results show that inflation has the greatest impact on income inequality of the first, second, third, fourth, seventh and eighth deciles. Bank interest rates and GDP have led to income inequality in the fifth and sixth deciles. Foreign direct investment also has the greatest impact on the income inequality of the ninth and tenth deciles. It also shows that the uncertainty of macroeconomic and foreign trade variables has increased the inequality of the first, second, third, fourth and fifth deciles more than the sixth, seventh, eighth, ninth and tenth deciles. These results are important in terms of macroeconomic planning, including controlling inflation, as well as preparing and creating the necessary economic conditions to benefit from foreign trade relations to reduce income inequality in the deciles.
On the other hand, the results show that the lower limit of the Gini coefficient of the first decile has a greater increase than the lower limit of the Gini coefficient of the second and third deciles. The lower limit of the Gini coefficient of the ninth and tenth deciles has increased more than the first eight deciles. The average limit of the Gini coefficient of the first and sixth deciles is higher than the average limit of the Gini coefficient of the second decile. The average Gini limit coefficient did not fluctuate significantly for other deciles. The upper limit of the Gini coefficient of the first, second, third, fourth and fifth deciles has increased more than the upper limit of the Gini coefficient of the sixth, seventh, eighth, ninth and tenth deciles. The results of this study, considering the inevitability of accompanying the process of economic globalization (foreign direct investment and the degree of economic openness), appear as a challenge for policy makers, and to solve this challenge, it is necessary to present and take the necessary solutions. . On the other hand, inflation is one of the important indicators of the instability of macro variables and has a dual effect on the distribution of income in society. In fact, inflation is considered as a subsidy for some people and as a tax for others as income to those who earn They are constantly harming and benefiting people who own capital, such as land, buildings, etc. Therefore, the government can have a special program for low-income or fixed-income groups by targeting them, including transfer payments, tax breaks, and for people who have more than they need, such as land and housing, through income tax. And the exponential wealth of individuals. These results are important in terms of macroeconomic planning, including inflation control for economic officials, as well as preparing and creating the necessary economic conditions to benefit from foreign trade relations to reduce the Gini coefficient of income deciles.