Degree probability function of the social network over time.

<p>The average probability distribution function (PDF) is in black. This PDF came from fitting by <i>Pk</i> ~ <i>k^ae^−bk</i>. The coefficients (95% confidence bounds) are as follows: <i>a</i> = 0.8199(0.7873, 0.8525), <i>b</i> = 0.1548(0.1506, 0.1589); goodness of fit (SSE) = 0.777 × 10⁻⁴; R-square = .9975, adjusted R-square = .9975, RMSE = 0.9141 × 10⁻³.