Additive and Multiplicative Decomposition

Here we will find the series of exports that have been supported by Procolombia from January 2009 to January 2022. Procolombia is a Colombian government company that seeks to support exports of non-traditional goods or services.

t=seq(2009.1,2022.2, length.out=length(Exportaciones_Mensuales_Procolombia$DATE))

Lets get a graph of the exports

export<-ts(Exportaciones_Mensuales_Procolombia$Monto,frequency=12,start=c(2009,1)) 
plot(export)

As expected, we see that exports tend to grow over time. We also see some peaks that show us seasonality.

Initial Decomposition

Lets try to get the components of the series. First i will use the additive decomposition model:

dec1<-decompose(export,type="additive")  
dec2<-decompose(export,type="multiplicative") 

plot(dec1, xlab = "Year")

Now lets use the multiplicative decomposition model:

plot(dec2, xlab = "Year")

I would choose to use the multiplicative model since the seasonal component tends to increase over time. I also think that we have to add more regresors in order to get a better forecast. Variables like exchange rate may have an impact on the exports.