Heston and Summers continued these comparisons and extended the estimates over both time and space in an effort that became the Penn World Table.
Heston is considered a leading world expert on international economic comparisons and purchasing power parity.
[3] In 1991, Heston co-authored with Summers a Quarterly Journal of Economics article titled "The Penn World Table (Mark 5): An Expanded Set of International Comparisons.
"[4] This article describes the Penn World Table as a set of national-accounts economic time series covering 138 countries.
The article introduced an updated, revised, and expanded version of the table with broader applicability to researchers, and was one of the most cited economic papers of the 1990s.