La de cal es que han crecido los nacimientos: La natalidad aumenta en Rusia pese a la crisis
La de arena es que podrían ser de musulmanes mayormente (Russia becoming a Muslim state?):
The fertility rate for Tatars living in Moscow is six children per woman, Mr. Goble said, while the Chechen and Ingush communities are averaging 10 children per woman. At the same time, hundreds of thousands of Muslims from Tajikistan, Uzbekistan and Kazakhstan have been flocking to Russia in search of work.
Russia’s Muslim population has increased by 40 percent since 1989, to about 25 million. By 2015, Muslims will make up a majority of Russia’s conscript army and by 2020 one-fifth of the population.