Performance metrics based on the size of US video ads saw a clearer trajectory than ad length. The larger the video ad, the higher the completion rate, with a 93.0% completion rate for extra-large video ads vs. a 66.0% completion for extra-small video ads. Clickthrough rates (CTR) also seemed to rise with video ad sizes. However, once ads were medium-sized or bigger, CTRs went up to at least 0.9% and continued to hover in that range. Read the rest at eMarketer.