Income Top Code Discrepancies OINCBUS

When comparing the documentation for the variable OINCBUS and OINCWAGE, specifically the section on their N.I.U., top, and bottom codes, with the entries for these variables in the IPUMS Top Code Tables, I notice a slight discrepancy between the sources. For the variable documentation, top codes for these variables are said to be 99997, while in the Top Code table, their top codes are said to be 99999.

From reading over some prior forum entries, I think the discrepancy amounts to a difference between top code replacements and top code thresholds. The 99999 value is the value that is the top code threshold: incomes that reach 99999 recoded to the top code replacement value of 99997. So if you have an income of 99999 then the observation’s value for that income variable is equal to 99997. Is this a correct assessment? Thanks for any clarifying information you can provide!

The top-code depends on the specific sample year for these variables. For both OINCWAGE and OINCBUS, the codes tab states that 99997 is the topcode for years 1988-1995 and for other years the topcode is specified in the Topcodes Tables.