In "Is Piketty's Second Law of capital fundamental?" by Per Krusell and Anthony A. Smith Jr the authors say, in a footnote:
Specifically, from the FRED database, we use series A023RX1A020NBEA on real gross national income, series W206RC1A156NBEA on gross saving as a percentage of gross national income, and series W207RC1A156NBEA on net saving as a percentage of gross national income. These series all come from the Bureau of Economic Analysis; with them, it is straightforward to construct a series for net saving as a percentage of net national income. (p737)
They say it is straightforward to construct a series for net saving as a percentage of net income. Can anyone explain how this series is constructed from the three given series?
The paper is available at http://www.jstor.org/stable/10.1086/682574 .