Certain numbers reveal the current evaluation of the economy. The health of the economy can be roughly viewed in terms of the financial health and confidence of 4 major components: consumers, banks, non-bank businesses, government.
Eg: Prices of critical commodities (like oil), value of index funds, growth in real estate prices, government debt, public debt.
Gross domestic product
As a summary
This is a measure of the total gross income of the country.
Comparison with GPA
Like the GPA in case of academia, it is a good summary, but it does not include finer details which could be gleaned from the whole data, such as how rich an average person feels.
Avoiding overcounting
To avoid double-counting and to include all services and goods which go into making a certain product, only end-consumption is considered. To avoid over-counting, money spent on imported goods is not counted - that contributes to the exporting country’s GDP.
Goods produced during previous years is not included in the GDP - even if they continue to be consumed. Instead, an imputed rent is included in the calculation.
Environmental costs
The costs to the environment from economic activity leading to growth is not included in the GDP. These costs arise from decreased life expectancy, greater sickness, lesser tourist pleasure etc.. Cost to life expectancy can be calculated based on the higher salary yielded by increased risk to life (around 60$ more for .0001 greater risk in 2011).
On the other hand efforts at spending to repair environmental damage gets counted - eg: environmental damage from BP’s oil spill is not included, but money spent on clean-up effort is!