I'm a proponent of it's ok to open outgoing links in a new window, but I can't find any arguments/data one way or the other within the last 4 years that doesn't reference 4 year old dogma. In the absence of recent analysis I rely on "what do the experts do" and this is what I've found:
sensible.com (Steve Krug) - generally doesn't open outgoing links in new window but link to amazon.com to buy books does open in a new window/tab.
cooper.com (Alan Cooper) - does open outgoing links in new tab/window.
www.nngroup.com - does not open links in new window.
google.com - does not open links in new window.
news.google.com, twitter.com, most emails, most forums - does open outgoing links in new window/tab.
wikipedia.org, stackexchange.com - does not open outgoing links in new window.
edit: found a recent analysis (courtesy of 3nafish): http://uxmovement.com/navigation/why-external-links-should-open-in-new-tabs/ and I agree completely.