Although the overall patterns emerging when averaging over many data sets can largely be explained in this way, there is also considerable variation across data sets that we do not yet fully understand, however.
we show that a greedy, left-to-right, arc-eager transition-based parser consistently performs worse when the dummy root node is placed at the beginning of the sentence (following the current convention in data-driven dependency parsing) than when it is placed at the end or omitted completely.