Exploring possible mechanisms of shortening.

<p>Annual values of <b>A.</b> median word length of all words, <b>B.</b> median word length of the 1000 most frequently occurring words, <b>C.</b> most frequent word length of the 1000 most frequently occurring words, <b>D.</b> fraction of 1000 most frequently occurring words relatively to all occurrences of words, <b>E.</b> median utterance length in number of words <b>F.</b> median tweet length in number of words, and <b>G.</b> median trending topic phrase length.