A simple data set drawn from World Bank Open Data. I'll use it to illustrate some merge issues you might encounter in panel data.
Format
A data frame with 4537 observations on the following 7 variables.
countryan English name for the country/territorial unit
iso2cthe two-character ISO code for the country/territorial unit
iso3cthe three-character ISO code for the country/territorial unit
yearthe year of observation
rgdppcthe real GDP per capita of the country/territorial unit in that year
lifeexpthe average life expectancy at birth for men and women for the country that year
hcithe human capital index for the country that year
Details
The idea for this data comes by way of a student encounter where we noticed this issue. Data were further generated by the wonderful WDI package. The underlying data come from the World Bank national accounts (GDP per capita), World Bank analyst estimates (human capital index), or the United Nations Population Division (life expectancy at birth).
The human capital index is on a 0 to 1 scale.