Journal Articles – E-prints – Astronomy
Submitting your paper as e-print on arXiv has become common practice in astronomy and astrophysics. A more in-depth analysis can be found my article Effect of E-printing on Citation Rates in Astronomy and Physics. Below you’ll see a diagram that extends figure 1 from this paper.

Fraction of E-printed Articles in the 4 main astronomy journals, Solar Physics, Icarus and Physical Review D
The European journals (A&A, MNRAS) seem to have reached a level of saturation, while ApJ and AJ still show a small increase. There is still growth in Solar Physics and Icarus, although e-printed articles are still a minority. This is in part a cultural effect. Physical Review D was added because it has a large astrophysics component.