In simultaneous equation theory a sample is said to be undersized when it is smaller than the number of exogenous variables. The sample moment matrix of these variables is then singular, but equations can nevertheless be estimated when different moments (hybrid moments based on the...

Our objective is to "explain" per capita GDPs by the countries' latitude, using PPP-based data for 138 countries in 1985 (PPP = purchasing power parity). A simple approach is formulated which nevertheless accounts for as much as two-thirds of the variance of the per capita GDPs.

Purchasing power parity-based data for gross domestic products are used to assess the affluence of the G-7 countries in the period 1885-1994. A simple Cobb-Douglas model is developed for the eligibility to this Group of Seven.