You can also have violence without death. Guantanamo and Abu Ghraib are examples. Because these people are only tortured, and not murdered, is that considered "peaceful"?
And it also would depend on how far back you draw the data from. Is the Stalin famine of the 30s modern, or ancient? If we cast the data back to the 1600s, it's new. If we cast the data back to the 1920s, its old.
Some data sets in this article go back to the 60s, some go back to the 30s, some only back to the 90s. Maybe we need more data. Lets cast all the data sets back a few hundred years and look again.
Consider me unconvinced.