Complex sentence: All three metrics also had a highly significant correlation with real gross domestic product per capita (RGDP/Cap); the Corruption Perceptions Index correlation with RGDP/Cap was the strongest, explaining over three fourths of the variance.
Split into simpler sentences: All three metrics also had a highly significant correlation with real gross domestic product per capita (RGDP/Cap). The Corruption Perceptions Index correlation with RGDP/Cap was the strongest, explaining over three fourths of the variance.