A simple consequence of these facts is that children have to learn about 7 to 10 words a day, every single day, to arrive at observed vocabulary levels by the time they are 20 years of age. And indeed empirical estimates of vocabulary growth in late elementary through high school are consistent with this rate. How do children achieve this rate of vocabulary growth given their daily experiences during this period? We know that most of this growth is not happening through direct vocabulary instruction in school since these methods are largely ineffective, and are not deployed at a rate that would result in the reliable acquisition of words at the required rate.