Bellugi and Fischer (1972) studied the rate of articulation in sign and speech and found that the rate of words per second was higher for spoken English than for American Sign Language. However, a proposition took about the same amount of time to produce in either sign or speech. Myers et al. (2011) conducted a follow up study with an explicit quantification method for measuring communicative efficiency in sign and speech. They proposed that communicative efficiency should be addressed both as representation efficiency (propositions per syllable) and as transmission efficiency (propositions per second). Following Myers et al. (2011), this study investigates communicative efficiency in sign and speech with a focus on changes over time. Narratives from TSL signers and Mandarin speakers were elicited using a picture story book. Comparing the data collected in 2005 and 2015 from the same participants, Taiwan Sign Language showed a slight increase in both transmission efficiency and representation efficiency after ten years, while Mandarin had a slight decrease in transmission efficiency and no change in representation efficiency. Statistical analysis showed that Taiwan Sign Language changed significantly more than Mandarin overall, but the difference in the direction of change across languages did not quite reach statistical significance. Since all participants were middle-aged throughout the duration of the study (maximum age was 53 for the Taiwan Sign Language group and 50 for the Mandarin group), the weak longitudinal effect is not surprising. A study with elderly participants (over 65) is needed to further explore the effect of aging on communicative efficiency.