In this paper, the phrase tax rate transparency describes the ease with which decision-makers can determine the rate at which their income is taxed. Prior experimental research has demonstrated that increased tax rate transparency results in better decisions (Rupert and Wright 1998; Rupert et al. 2003; Boylan and Frischmann 2006). This study contributes to our understanding of the effects of tax rate transparency by providing evidence on its distributional consequences. More specifically, this study provides evidence on who benefits from tax rate transparency, particularly when some individuals have access to better information about tax rates than others. Of particular interest is how those with limited access to information about tax rates fare in comparison to those who may have better information about relevant tax rates, and whether the private information that informed parties possess leaks out to the uninformed over time.Understanding the effects of tax rate transparency is important because a lack of transparency can cause decision-makers to miscalculate the potential tax effects of planned transactions. This can lead to strategic and tactical errors, and potentially reduce profits. It also creates incentives for decision-makers to use scarce resources to attempt to overcome the lack of transparency, which, in turn, can create distributional consequences in an economy. In addition, a lack of transparency often creates calls for tax reform as a means of promoting increased fairness and reducing the burden associated with measuring one's tax liability.This paper reports on a set of experimental markets in which participants were required to generate after-tax trading profits sufficiently large to generate a specific return on investment. Each market lasted eight periods, and the degree to which the relevant tax rate was transparent to participants varied across markets. Consistent with prior research, the results indicate that a lack of tax rate transparency had a negative effect on profits earned in the markets. Greater transparency led to higher profits for those who had access to the information about the relevant tax rate. However, the results from the experiment add to the existing literature by documenting that the effect of greater transparency spilled over to those who did not have access to the information about the relevant tax rate. It was those participants who benefitted the most over the course of the experiment—simply by participating in markets in which the tax rate was transparent to others.More specifically, data from the experiment show that when the tax rate was transparent to at least some of the participants, those participants earned anywhere from 14 percent to 45.4 percent more profit than they would have in markets in which the rate was not transparent to anyone, with specific amounts depending on whether the rate was transparent to everyone or only to some participants, as well as on the stage of the markets (early periods, middle periods, or late periods). In markets in which there was a mix of informed and uninformed participants, the increased profits earned by participants for whom tax rates were made transparent spilled over to the uninformed participants. It was these uninformed individuals who gained the most over time. Initially, their profits were about 20–25 percent lower than the profits of those who were informed (but still about 9 percent higher than profits earned in markets in which tax rates were opaque for everybody), but by the late periods of the markets, their profits were virtually indistinguishable from the profits of those for whom tax rates were made transparent.This research may be of interest to policymakers, who must wrestle with tradeoffs associated with adopting new tax rules. Some rules might influence behavior in ways that policymakers desire, but at the same time make tax rates less transparent and, hence, generate undesirable side effects. Alternatively, the effects of tax simplification will depend, at least in part, on the degree to which individuals are able to deal with complexity on their own. Policymakers should be aware of these tradeoffs when considering altering tax rules.