hello. 3 suggestions. I) use eviews to perform a principal component analysis - very simple to execute with the software. ii) use error correction (and cointegration to test validity of long run trend) iii) if you want to keep things super simple, just use correlation analysis. depending on your time frame, you could use either 3m or 12m rolling correlations to get a sense of which factor is generally strongest and crucially to get a sense of the dynamics. eg factor 1 might have a long run correl of 0.8, but has a tendency to oscillate seasonally and even go negative. hope that's useful.