Internal Revenue Code §183 generally prohibits taxpayers from deducting expenses related to activities in which the taxpayer is not primarily motivated by profit. The applicable Treasury Regulation provides nine specific factors to consider in determining if a taxpayer's activity is motivated primarily by profit. This paper reviews the United States Tax Court's application of the nine factors in a sample of decisions reported between 2005 and 2015, inclusive, investigating potential inconsistencies between the Regulation language and observed outcomes. We find that a taxpayer successfully demonstrating three factors has a 158 percent greater probability of winning than a taxpayer demonstrating only two factors. We also observe that operating in a businesslike manner is a key factor to taxpayer success. Finally, we show that pro se taxpayers generally fare worse than represented ones, although the marginal reward to an additional favorable factor may be higher for them than for represented taxpayers.