This figure depicts perhaps the strongest evidence for the importance of literacy in job performance. The figure shows three groups of military workers having reading grade levels of 4-6.9, 7-8.9, or 9-1 1.9 on the horizontal axis. There are two types of workers, Supply Specialists and Automobile Repairman (mechanic). The filled points show how well workers performed actual job sample tasks in a test situation. The performance of Supply Specialists increased from around 42% for those reading in the lowest group, to 48% for those reading above the 9th grade level. The Repairman data show no relationship to reading. These differences in Supply Specialist and Repairman may reflect the fact that the Supply Specialists job tasks are inherently demanding of reading to complete forms, requisitions, etc. while the Repairman's tasks, such as adjusting the carburetor, repairing the brakes, etc. do not inherently demand reading. However, as the data points indicate, when either Supply Specialists or Repairman used the available technical manuals to aid in the performance of their job tasks, proficiency increased across all three reading groups. The top, solid line shows the average for the two jobs. The effects of both having higher levels of reading skill arid using that skill on productivity as measured by the performance of actual job tasks can be seen by comparing the average correct scores of those in the lowest reading group who did not use their manuals (average of 45% correct), to that of those in the highest reading group who did use their manuals (average of about 65% correct). This represents about a 20% increase in productivity due to both having and using higher levels of literacy (reading).