The article provides a brief history of the emergence of demographic forecasts, shows their use by the United Nations, the range of countries for which forecasts were made and are being drawn up, considers demographic forecasts that were carried out during the Soviet era and provides a detailed analysis of demographic forecasts for Russia. In contrast to the forecasts of the population of the Soviet Union as a whole, for Russia they initially began to focus on the downward dynamics. It is concluded that over two decades (1996-2015) in countries with a predominance of the Slavic ethnos (excluding the former republics of Yugoslavia), the population as a whole has decreased to 95.5%, while in countries with a predominance of the Anglo-Saxon ethnos — it increased to 123.8%. The forecasts given in the article are compared with the actual size of the population that has already taken place. Everywhere in countries with a predominance of the Slavic ethnos, the actual population is higher than the predicted, and in countries with a predominance of the Anglo-Saxon ethnos, on the contrary. Comparing the forecasts with the actual population dynamics, the conclusion is substantiated about a noticeable change in the ratio between the two groups of countries united by ethnicity, a decrease in the demographic potential of the Slavic group and its increase in the group with a predominance of the Anglo-Saxon ethnos. In the final part of the work, it is said that the presented rates of change in the population size in 35 years and then in another 50 years, arising from the UN demographic forecasts for 2050 and 2100, as well as the demographic dynamics in the 90s of the twentieth century and in the first 15 years of the new century, indicate that if Russia, like other Slavic countries do not make radical efforts and, accordingly, do not consistently take effective measures to change the demographic trends, then the same thing can happen to Russia as has happened in different centuries to many countries such as Assyria, the Hunnic Empire, etc. The current geopolitical situation in which Russia is, its status as a great power, the country's largest territory in the world, favorable geographical position and colossal natural resources, dictate the need to increase its economic, defense and, naturally, demographic potential.