Overlap reduction function obtained with the optimal statistic. Purple circular and orange squared points indicate the results for the injGWB02 and injCGW5 datasets respectively. The correlation coefficients for each pair of pulsars are grouped in 10 bins of 30 pulsar pairs each, the points represent the weighted average in each bin. The solid line shows the expectation value of the HD correlation. Note that the purple rightmost point lie below the orange one.