\({\text{edge\ loyalty}=\ \theta}_{i}^{t-1,\ t}=\ \frac{{|Y}_{i}^{t-1}\bigcap\text{\ Y}_{i}^{t}|}{{|Y}_{i}^{t-1}\bigcup\text{\ Y}_{i}^{t}|}\backslash n\) (2)