In this paper we studied the effect of the economic and social factors in the global decline of mortality levels. These factors include: the real per capita income, the daily calorie supply, the adult literacy rate for males, the adult literacy rate for females, the number of Population per physician, the percentage of population living in urban areas, the percentage of population with access to health services, and the percentage of population with access to safe water; are the available variables which we used for their possible influence in mortality levels. On the other hand, and among many mortalities measures we used Infant Mortality Rate because it is more likely be affected by these socio-economic variables than other mortality measures. Based on our data, which were collected form the periodicals of the United Nations, the empirical findings showed that all the investigated variables are highly correlated with IMR, with correlation-coefficients greater than and equal 0.7 for all. The number of Population per doctor is the sole variable that turned out to be positively related with IMR. For the multiple regression of mortality on these variables we found that: the log of the real per capita income, the adult literacy rate for females, and the percentage of population having access to safe water are the only variables which turned out to be statistically significant. The diagnosis we made did not confirm the absence of 'multicollinearity' problem. Accordingly, a remedy for 'multicollinearity' was suggested using the Principal Component Analysis to extract independent factors to represent the data. The first extracted factor is shown to be interpreted as a contrast between the log of the number of Population per doctor and the rest of the variables. It explained about 87% of the variations in mortality. The study showed a significant difference between the developed and the developing countries concerning mortality levels and concerning the extracted factors using the PCA. The factor analysis technique showed that all the socio-economic variables turned out to be represented by one and only one factor. This factor is identified, without any doubt, to be the infant mortality. This means that mortality reductions are more likely to happen with the economic development and consequently with improving health and medical technology, along with the better diet and greater educational attainment and awareness of health protection as an auxiliary factor.