Why are Bond's girlfriends dying lately?

I was looking at an article on violence in Bond movies over the years (chart) and in the comments left on the article, a poster noted that in all of the new Bond movies, the most important women to the plot are killed.

I don’t recall this from old Bond movies (there was a woman killed offscreen in Goldfinger, but that is the only one I can recall).

Is this trend indicative of something changing in our culture for women? If there is a trend in how we are treating women in our culture, is it a positive or negative change?