I'm looking at the Penn World Table 9.0 data, and find that the "Share of merchandise imports at current PPPs" (csh_m) can be negative. For example,

   country  year  csh_m
   <chr>   <dbl>  <dbl>
 1 Aruba   1970. -0.485
 2 Aruba   1971. -0.459
 3 Aruba   1972. -0.436
 4 Aruba   1973. -0.441

My initial thought is that the share of import (csh_m) here actually means "net import as share of GDP." However, this is not correct, because share of import (csh_m) and share of export (csh_x) don't have the same magnitude.

   country  year  csh_m csh_x
   <chr>   <dbl>  <dbl> <dbl>
 1 Aruba   1970. -0.485 0.427
 2 Aruba   1971. -0.459 0.435
 3 Aruba   1972. -0.436 0.441
 4 Aruba   1973. -0.441 0.477
  1. Where can I find documentation explaining the construction of csh_m and csh_x from the Penn World Table?

  2. If a want to construct a variable of trade openness, should I add the absolute values of csh_m and csh_x?

  • $\begingroup$ Have you looked at p3 of rug.nl/ggdc/docs/national_accounts_in_pwt80.pdf ? If it's only very small countries, could it be that statistical discrepancies are larger than imports? $\endgroup$
    – Dan
    Commented Mar 15, 2018 at 17:39
  • $\begingroup$ All the csh_m (Share of merchandise imports at current PPPs) numbers in that table for all years and all countries are negative (apart from some years for Bermuda) while all csh_x (Share of merchandise exports at current PPPs) are positive (again except for a few years for Bermuda). These shares look like $Y=C+I+G+X-M+R$ all divided by $Y$. Places with big absolute values seem to include Hong Kong, Singapore, BVI, Malta, Turks & Caicos, where trade is indeed open. So you could add the absolute numbers together $\endgroup$
    – Henry
    Commented Aug 5, 2019 at 22:28
  • $\begingroup$ See rug.nl/ggdc/productivity/pwt and the legend tab of the Excel spreadsheet for more explanation about the data $\endgroup$
    – Henry
    Commented Aug 5, 2019 at 22:30


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