<P> Debt held by the public was $15.05 billion or 16.5 % of GDP in 1930 . When Franklin D. Roosevelt took office in 1933 , the public debt was almost $20 billion , 20 % of GDP . Decreased tax revenues and spending on social programs during the Great Depression increased the debt and by 1936 , the public debt had increased to $33.7 billion , approximately 40 % of GDP . During its first term , the Roosevelt administration ran large annual deficits of between 2 and 5 % of GDP . By 1939 , the debt held by the public had increased to $39.65 billion or 43 % of GDP . The buildup and involvement in World War II during the presidencies of F.D. Roosevelt and Harry S. Truman led to the largest increase in public debt . Public debt rose over 100 % of GDP to pay for the mobilization before and during the war . Public debt was $251.43 billion or 112 % of GDP at the conclusion of the war in 1945 and was $260 billion in 1950 . </P>
when has growth in the national debt been highest
The buildup and involvement in World War II