The title pretty much. I mean they suffered 10,130,000 deaths in total (incl military and civilian) in the space of only 20 years apart from both wars.
The German Federal Statistics Office has a wonderful animation about this.
The war created a huge demographic hole in Germany, with a huge number of "missing men" between the ages of ~20 and ~40 when the first postwar census was conducted in 1946. This, coupled, with a dip in the population around the age of 15 (due to lower birth rates during the Great Depression), and another, older dip correlating to lower birth rates and loss of lives during World War I, set the stage for German demographic patterns in the future.
Germany's total population reached its 1939 levels by 1950, but this represented a Germany with an adult population clearly skewed towards women. (Indeed, after the war there was a great deal of concern about this in Germany; one poster in Berlin drew attention to the fact that there were 1800 women for every 1000 men in some neighborhoods). This, combined with the fact that so many men were in POW camps, injured, or otherwise unavailable for work, had a huge impact on the German labor force. In the immediate aftermath of the war, women became the symbol of efforts to dig out and rebuild. "Women of the rubble" remain a classic image of the immediate postwar period, with teams of women clearing rubble by hand from the streets of Germany's cities.
The two postwar German societies already emerging in the late 1940s viewed this situation very differently. In the West, women's contributions provided some of the justification for the protection of women's rights when the Grundgesetzt (Basic Law) was drawn up for the Federal Republic in 1949. However, their work was also seen as a hardship, as women contributing in a crisis; conservative West German society tended to see the ideal as a return to roles as wives and mothers once men were back on the job. In the East, by contrast, where the situation was if anything more dire, women's efforts were not viewed the same way; rather, women were equal and belonged in the workforce, even if they should also be wives and mothers.
Birthrates increased for the first decade after the war, but that provided no immediate help. And (West) Germany needed the manpower (and they did think of it as manpower), as rebuilding quickly set the stage for the economic miracle that saw the West German economy explode in the 1950s and 1960s. To meet the need for labor, the Federal Republic signed a series of agreements with other states to recruit workers to come live and work on a temporary basis in West Germany. The first of these Gastarbeiter (guest worker) agreements were signed with Italy (1955), Spain (1960), Greece (1960), and most famously Turkey (1961). Later agreements were also made with Morocco (1963), Portugal (1964), Tunisia (1965), and Yugoslavia (1968).
Despite the influx of guest workers each year, with some 600,000 new workers arriving each year at the program's height in 1970, the shortage of labor remained a factor in the west, with unemployment below 1% throughout most of the 1960s and in 1970 and 1971. (The economy turned in the 1970s, leading to the end of guest worker agreements, though many, especially the large population of Turkish guest workers, remained in West Germany.)
Beginning in 1963 the German Democratic Republic also had agreements in place to recruit labor from fellow socialist states (including Poland, Mozambique, and Cuba), though here the need was not so much a product of incredible economic growth--East Germany did not enjoy the same sort of economic miracle as West Germany, though by eastern bloc standards the East German economy incredibly successful--but rather to combat the drain on the East German labor force from years of movement from East to West prior to the construction of the Berlin Wall in 1961 and similar provisions along the inner-German border.
Although the German population reached its pre-1939 levels by 1950, its growth would be hampered by the impact of World War II. Following the Great Depression, there was something of a baby boom in peacetime Nazi Germany, thanks in no small part to Nazi policies encouraging (Aryan) German women to have children (see, for instance, the Mothers Cross medal, subsidies for families, etc.) The large population of children born during these years (1933-1939 and even into 1940 and 1941) came of age in the second half of the 1950s, and thus we see birthrates rising from 1955 to a peak in 1964, with over 1.3 million Germans born that year, nearly matching the peak in 1940 (falling short by 30,000 births).
However, after 1964 the birthrate began to drop again. At this point, the significantly smaller generation of Germans born during and immediately after the war were beginning to have families, and with less of them to have families, correspondingly fewer children were born. The economy of the 1970s only exacerbated this trend. Indeed, the number of births in 1945 and 1975 were nearly identical, with right around 750,000.
From that point, the German birthrate did recover some, before going into a long slow decline after the 1980s. This is the result of not only an aging population in Germany, but cultural shifts re: family, the number of children families have, the availability and use of contraceptives, etc.
In addition to the link above, see: