Final answer:
Based on eMarketer.com data from 2014, outdoor advertising is part of the final third of total ad spending, which includes direct mail, magazines, yellow pages, and billboards. The exact percentage for outdoor advertising isn't given, but it is smaller than the leading methods, hinting it's less than 10%.
Step-by-step explanation:
According to data from eMarketer.com, in the year 2014, the U.S. economy spent roughly $180.12 billion on advertising. The spending was distributed among various advertising mediums, with about one third going to television commercials. Another third of the budget was split fairly evenly between internet, newspapers, and radio. The final third covered other methods including direct mail, magazines, telephone directory yellow pages, and billboards. Within this context, outdoor advertising, such as billboards, would be part of the last third of the total ad spend. Although exact percentages for outdoor advertising alone are not detailed, it can be inferred that outdoor advertising would represent a smaller fraction compared to larger sectors like television and digital. Therefore, it would likely be under 10%, making option 1 the most plausible answer without the exact figure.