In Daryl F. Mallard, Jason L. Anthony and Kari L. Woods' research paper, "Understanding oral reading fluency among adults with low literacy: Dominance analysis of contributing component skills," factors impacting fluency are analyzed. They looked at two definitions of fluency- one quantified by correct words per minute (cwpm) and the other comprehension based.
What they found was that the number one factor that influences fluency is word reading efficiency. If looking at only cwpm and processing speed was the second most influential factor followed by vocabulary. If comprehension is included in the analysis, then vocabulary is the second most influential factor followed by auditory working memory. Phonemic awareness and phonetic decoding were both relatively of little importance. What was virtually noninfluential to reading skills was nonverbal IQ scores.
What does this research mean to us, the practitioners? One thing it means is that as our students age, we need to shift from teaching decoding and phonemic awareness to sight word recognition and vocabulary development. Since we need reading to include comprehension, we need to focus on skills that influence comprehension such as fluency and vocabulary.
It means that high quality vocabulary instruction is essential. This is not news. We know that vocabulary is the number one determinate of comprehension. The Common Core stresses the importance of academic vocabulary. I am constantly surprised at the words my students do and do not know. They do not know words I regularly use in my oral vocabulary. This means that when they listen to teachers, they are confused by instruction but will rarely ask questions about it for fear of looking dumb. One of the contributing factors could be related to auditory processing and working memory. The average kindergartener can understand 90 words per minute. (This is why kindergarten teachers talk in that slow rhythmic manner- so their students can follow what they say.) The average high school student can comprehend 150 oral words per minute. When we speed our talk up beyond that level they loose words and meaning. Students with limited processing speeds or auditory working memory need us to speak more slowly than their peers. Students who are struggling readers may not benefit from the vocabulary we use, if we speak too quickly. If we speak more slowly, we may increase comprehension and meaningful exposure to vocabulary. This can help them read in general and in their school achievement in specifics.