Public spending and wealth growth

In researching a paper I'm writing I came across this chart on the impact of public spending on economic growth.

What this says is pretty clear. Excessive government robs the economy (and citizenry) of economic growth. The difference between 6.6% growth (small government) and 2.0% growth (large government) compounded over 20 years is HUGE. For the record Australian GDP is between 35% and 40% (middle size government).

Why is it so? Government spending is inefficient but at the lower levels necessary. Government spending for law and order, defence, justice etc creates the economic and social security an economy needs to prosper. Beyond that level government takes wealth (capital) from private individuals to 'consume' on low-productivity investments. The economy is denied that the economic benefits of the productive investment that would have been made by private profit seeking individuals. The more the government spends, the greater the economy suffers from a growth perspective.

Don't believe? This data is from over 30 countries over a multi decade period. Practically irrefutable. What is the best government? One that simply provides security and gets out of the way.