How stable are the impact factors of major astrophysics journals

We examine the long-term trends in impact factor over the past decade (2015-2014) for seven flagship journals widely used in Astrophysics: ApJ, AJ, ApJL, ApJS,A &A, JCAP, and MNRAS. We check the variation of both the traditional impact factor as well as the median-based impact factor, which we had studied in a previous work. We find that ApJS exhibits the largest drop in impact factor from 14.9 to 9.0, while ApJ and MNRAS show a steady decline from 6.7 to 5.2 and 5.6 to 5.0, respectively. However, the impact factors for AJ and ApJL have shown a steady increase from 4.55 to 5.35 and 6.4 to 9.7, respectively. The median-based impact factors are much more stable showing variations of at most $\pm 1$ within the last decade.