Citation count in each year was normalized to the maximum citation counts of the time period. The equation $C_{i}^{Norm}=\frac{C_{i}}{C^{max}}$ was used to calculate the normalized citation in a year, in which $C_{i}$ is the citation count in year i and $C^{max}$ is the maximum number of citations in the 5-year time period. As the normalized citation count is not enough to look at the trends of citations before and after the inclusion year, propensity was also calculated. To do this, $R_{i}^{Norm}$, the normalized random citation count was first calculated using the equation $R_{i}^{Norm}=\frac{R_{i}}{R^{max}}$ in which $R_{i}$ is the random citation count in year i and $R^{max}$ is the random maximum citation count in the 5-year time period. This was then used to calculate propensity through the equation $P_{i}=\frac{C_{i}^{Norm}}{R_{i}^{Norm}}$. When $P_{i}$ is equal to 1, the citation count of the articles is what is expected by chance. When $P_{i}$ is greater than 1, the citation count is greater than what is expected, and when $P_{i}$ is less than 1, the citation count is less than what is expected.