I am attempting an multilevel analysis looking at political trust across different countries. For my level 2 contextual independent variables I will be using macroeconomic data such as GDP growth, inflation, unemployment, GDP per capita. I look to see how much macroeconomic performance can explain variance in political trust between countries. I am unsure on how I should treat these variables. I have read literature saying you shouldn't center these variables, other literature says you should. Right now the data is in its raw form, e.g. GDP per capita ranges from \$17000 for one country to \$85,000 for another country. GDP growth ranges from 0.9% to 11%. Unemployment ranges from 2% to 15%. When I run the regression with the raw figures in Rstudio I get this message
Warning: Some predictor variables are on very different scales: consider rescaling
What would be the best way to treat these variables, would it be to rescale them? Standardize them or center them? I am using Rstudio for this analysis and would appreciate recommendations on r functions to use as I am new to stats.