How are the income quintiles created?

If there are five equal categories, why do they appear unequal?

The quintiles were created using a weighted STATA command. Please note: Since income is a household, not an individual, characteristic, the income quintiles are weighted quintiles of households, not of individuals. In addition, there is a zero category to the quintiles that includes negative incomes and those below 1000R.
The top quintiles have more individuals because high income households tend to have more individuals.
For households with income of R1000 or greater, if you sort the individual file by household id, and select only the first individual in each household, you will get almost exactly the same number of individuals/ households in each quintile.