I have done seasonal adjustments on different economic data in R using x13 (default specification=RSA5c) RJDemetra package. Some of my variables show additive and some show multiplicative seasonality but I am not able to identify the reason and how its decided. I believe its sorted to multiplicative or additive in the decomposition step but does anyone know how its determined?
I would really appreciate some help I have tried reading the package manual but still haven't found an answer.
this is the code I use to decompose the data in R
oilsax13$decomposition