Hi everyone,
I only have a small doubt, I am calibrating my model by the method of moments, adjusting certain parameters to the great ratios, these are: internalpublicdebttoGDP, externalpublicdebttoGDP, consumptionto GDP, TradebalancetoGDP, GovernmentInvestmenttoGDP, etc.
When calculating these proportions from the data in quarterly frequency, (after adjusting for seasonality), I find that their behavior is not stationary, in many cases there appear to be trends. My questions are:

Is it still valid to take the average of these series as steadystate values?

I was thinking that since they are steadystate values it is better to obtain the trend component of each of the variables and divide it by the trend component of GDP, (using onesided HP filter). Could this be a better option?
Thanks in advance.