According to the paper linked by the original announcement [1], the parser scores 94.41% for unlabeled attachment on the Wall Street Journal corpus [2], a parsed and labeled data set of 30 million words.<p>This corpus is a standard for NLP research on english syntax, but I think its worth remembering there is a great deal of disagreement among linguists about what the syntax of english is and what the lexical categories are.<p>[1] <a href="http:&#x2F;&#x2F;googleresearch.blogspot.com&#x2F;2016&#x2F;05&#x2F;announcing-syntaxnet-worlds-most.html?m=1" rel="nofollow">http:&#x2F;&#x2F;googleresearch.blogspot.com&#x2F;2016&#x2F;05&#x2F;announcing-syntax...</a>
[2] <a href="https:&#x2F;&#x2F;catalog.ldc.upenn.edu&#x2F;LDC2000T43" rel="nofollow">https:&#x2F;&#x2F;catalog.ldc.upenn.edu&#x2F;LDC2000T43</a>