NFL sports gambling markets are efficient if one strategy is not consistently profitable year after year. The analysis in this paper examines the efficient market hypothesis using the home-underdog theory. The data were collected for home-underdogs for the last 10 NFL seasons. Important filters were applied to examine potential variations of the home-underdog theory that may be profitable. There was no variation of the home-underdog theory that was consistently profitable year after year. There were 5 different variations that were profitable in the 10 years, but they were not profitable every year. The results provide evidence that the NFL sports gambling markets are efficient. Strategies that are profitable one year will not be in other years as sportsbooks become more aware of them
