I was trying to rationalize it this way: 1980's - first decade 1990's - second decade 2000's - third decade 2010's - fourth decade I guess, technically, th

I was trying to rationalize it this way: 1980's - first decade 1990's - second decade 2000's - third decade 2010's - fourth decade I guess, technically, the third decade of age for this paper ended in 2016, making 2017 the fourth. But this seems like silly ways to rationalize it. Genuinely seems like a typo.