add_cow_trade() allows you to add Correlates of War trade data to your
(dyad-year, leader-year, leader-dyad-year, state-year) data frame
Value
add_cow_trade() takes a (dyad-year, leader-year, leader-dyad-year, state-year) data frame and
adds information about the volume of trade in that given dyad-year or state-year. For the state-year (leader-year)
data, these are minimally the sum of all imports and the sum of all exports. For dyad-year (leader-dyad-year) data,
this function returns the value of imports in current million USD in the first country from
the second country (and vice-versa) along with their "smooth" equivalents.
Details
For the dyad-year (and leader-dyad-year) data, there must be some kind of information loss in order to work within the limited space available to this package. This package loads a truncated version of the data in which the trade values are rounded to three decimal points in order to greatly reduce the disk space for this package. I do not think this to be terribly problematic, though I admit I do not like it. If this is a problem for your research question, you may want to consider not using this function for dyad-year or leader-dyad-year data.
Be mindful that the data are fundamentally state-year or dyad-year and that extensions to leader-level data should be understood as approximations for leaders (leader-dyads) in a given state-year (dyad-year).
References
Barbieri, Katherine, Omar M. G. Keshk, and Brian Pollins. 2009. "TRADING DATA: Evaluating our Assumptions and Coding Rules." Conflict Management and Peace Science. 26(5): 471-491.
Examples
# just call `library(tidyverse)` at the top of the your script
library(magrittr)
# The function below works, but depends on running `download_extdata()` beforehand.
# cow_ddy %>% add_cow_trade()
create_stateyears() %>% add_cow_trade()
#> Joining with `by = join_by(ccode, year)`
#> # A tibble: 17,121 × 5
#> ccode statenme year imports exports
#> <dbl> <chr> <dbl> <dbl> <dbl>
#> 1 2 United States of America 1816 NA NA
#> 2 2 United States of America 1817 NA NA
#> 3 2 United States of America 1818 NA NA
#> 4 2 United States of America 1819 NA NA
#> 5 2 United States of America 1820 NA NA
#> 6 2 United States of America 1821 NA NA
#> 7 2 United States of America 1822 NA NA
#> 8 2 United States of America 1823 NA NA
#> 9 2 United States of America 1824 NA NA
#> 10 2 United States of America 1825 NA NA
#> # ℹ 17,111 more rows