The NIPA measure is useful in explaining how government saving has affected net national saving available for investment.
A useful measure to explain how net national savings available for investing has been affected by government is the NIPA measure. 
mnli hypothesis: A useful measure to explain how net national savings available for investing has been affected by government is the NIPA measure.  premise: The NIPA measure is useful in explaining how government saving has affected net national saving available for investment.