Traditionally, a single asterisk indicates significance at p < .05, two asterisks indicate p < .01, and three indicate p < .001. After decades of such usage, with style manuals indicating it as the preferred usage, and with other social sciences using the same system, one might consider the standard of one asterisk for .05 set in stone. However, in the past decade the use of asterisks has changed in political science.
Today, frequently, one asterisk means p < .10. The magic level of p < .05 that used to receive an asterisk now receives two, and .01, which used to get two asterisks, now gets three. I call it asterisk inflation.
See the full article by Joshua Goldstein.