World War I US Defense Spending

DURING WORLD War I defense spending in the United States exploded from less than one percent of GDP in 1915 to a peak of 14 percent in 1919 and then back down to one percent by 1923.
But the data series of “Series Y 605-637. Federal Government Expenditure, by Function: 1902 to 1970” in the Census Bureau’s Historical Statistics of the United States: From Colonial Times to 1970 only tabulates federal spending for 1913 and 1922, completely missing out on the years of World War I.
But the Census Bureau does publish annual federal government expenditures in another table, “Series Y 457-465. Outlays of the Federal Government: 1789-1970 Series Y 466-471. Outlays of the Federal Government, by Major Function: 1900-1939.” The problem is that the numbers in the two Census Bureau tables don'’t match up.

Comparison of World War I Defense Spending (millions of dollars)
Spending Item	1913	1914	1915	1916	1917	1918	1919	1920	1921	1922
Census Bureau Numbers from “Series Y 605-637. Federal Government Expenditure, by Function: 1902 to 1970”
Total Spending	970									3,763
Total national defense	250									875
Military services only	245									864
Interest	23									988
Census Bureau Numbers from “Series Y 457-465. Outlays of the Federal Government: 1789-1970.” Series Y 466-471. Outlays of the Federal Government, by Major Function: 1900-1939. Updated: 4/15/2015
Total Spending	715	725	746	713	1,954	12,662	18,448	6,357	5,058	3,285
Major national security	293	298	297	305	602	7,110	13,548	3,997	2,581	929
International affairs and finance	5	5	5	6	591	4,748	3,500	435	83	10
Veterans services and benefits	175	173	176	171	171	235	324	332	646	686
Interest	23	23	23	23	25	198	616	1,024	749	669

You can see the problem. The entire war spending effort is missing from the data series that we are using. And in 1913 and 1922 they don'’t match up.
We chose to fill in the missing numbers by matching the spending numbers from “Outlays of the Federal Government, by Major Function: 1900-1939” to the numbers on the incomplete “Federal Government Expenditure by Function: 1902-1970.” then track the trajectory of the numbers in the Outlays dataset. Here are the results:

Construction of World War I Defense Spending Dataset (millions of dollars)
Spending Item	1913	1914	1915	1916	1917	1918	1919	1920	1921	1922
Numbers interpolated from Outlay table shown in italic. Updated: 4/15/2015
Total expenditure	970	1,005	1,051	1,042	2,308	13,041	18,852	6,785	5,511	3,763
Total defense and intl	250	253	250	258	1,438	11,801	16,989	4,372	2,602	875
Military only	245	248	245	251	546	7,053	13,489	3,936	2,518	864
Interest	23	23	22	22	24	196	614	1,022	996	988

We have interpolated values for national defense and for total federal spending by applying the entire Outlays data items to the Expenditures table by adjusting all numbers so that they match the numbers in the Expenditure table for 1913 and 1922.

UPDATED: 4/15/2015