The growing complexity of the online video ad market means that advertisers now have a variety of ways to measure return on investment. But which method is best? This year, 36% of ad executives indicated that their clients placed the highest value on gross rating points (GRP) or target rating points (TRP) to measure the size of their audience. Still, another 30% said clients valued the percent of impressions that reached their target audience, while 24% named the percent of unique viewers in target. Read the rest at eMarketer.