Figure 7 plots the white and flicker noise amplitudes as a function of station latitude. In general, latitudinal effects are small. While there is a slight tendency for southern hemisphere stations to have larger noise amplitudes, the difference is small and not statistically significant. On the other hand, tropical sta- tions (between -23 ø and +23 ø latitude) clearly have higher levels of white noise in the vertical component compared to other sta- tions (Figure 7). The difference is statistically significant at 95% confidence. Four stations (FORT, GUAM, KOUR, and KOKB) are in this latitude band. Two of these (FORT and GUAM) are equipped with newer Turbo Rogue receivers, one (KOUR) is equipped with the older Rogue receiver and one (KOKB) experi- enced a receiver upgrade (Rogue to Turbo Rogue) midway through the time series studied here with no obvious effects (Table 1, Figure 3). Thus the difference is unlikely to be due to hardware differences.