The war of 1914-1918 (WWI) resulted, in France by a loss of approximately 2,850,000 inhabitants including 1,350,000 deaths of soldiers.
Those soldiers in 1914 were over 20 years old and would have been over 55 in 1950; this explains the disparity between the male and female population in 55 to 70 years old age in France in 1950.
i hope this helped <3