http://www.realclearmarkets.com/art...nt_spending_and_the_18_of_gdp_myth_99063.html
The truth here is that the U.S. has thrived with far less government spending. Indeed, a look at times when we as a nation were imperiled offers a far different story than what you have been told.
Research shows that from the founding of our nation, 1787-1849 (63 years) federal spending averaged 1.7% of GDP. For the next 51 years, 1850-1900 (including fighting the Civil War) spending averaged only 3.1%. From 1901 till 1930 (including fighting WWI) it never reached 8%, and averaged approximately 3.2%.
At the height of the progressive movement (including FDR's New Deal) federal spending as a percentage of GDP never went above the 1934 level of 10.7%. Even after the historic 1944 (WWII) level of 43.6%, spending had fallen by 1948 to 11.6% of GDP.
In short, for the first 130 years of the U.S.'s 224 year existence, federal spending as a percentage of GDP averaged around 2.5%!
So why is the 18-25% solution offered? At best politicians might be misusing or misrepresenting data, or using only a couple of decades for determining what's "historical" and "average" spending. In all honestly, heuristic ignorance and the need for political capital is probably driving the rhetoric. What's important is to realize the "parroting" we are hearing should be our canary in the mineshaft, warning us of the impending decline of our economy caused by excessive federal spending.
Why should we care? Because government spending is taken directly out of your pocket, or out of the economy. Spending is today's burden becaue every dollar consumed by our profligate government is one less that could fund productive advancement in the private economy.
Every dime needlessly spent by government comes at the cost of efficiency in moving scarce resources to their most valuable use. As Milton Friedman said, "nobody spends somebody else's money as carefully as he spends his own. Nobody uses somebody else's resources as carefully as he uses his own." So any policy that reduces personal freedom in economic decision making inhibits economic growth which forces people to suffer needlessly.