There is a large body of academic research that has been done on tax efficiency internationally, an awful lot of it looking at OECD countries and comparing the various tax systems and the effects. One lesson from the review of that literature is that consumption taxes are the least economically distortionary taxes to the economy. You see this across countries.
The United States is unique in not having a consumption tax. As a rule, economists prefer consumption taxes over personal income taxes and business taxes, although you have to address the aggressiveness of the impact of consumption taxes, in terms of the income distribution. You need to be sensitive to those issues.
Beyond that, however, the literature basically argues that the next least distortionary economic taxes are personal income taxes, and then the most distortionary are business taxes. Beyond that, it's a matter of figuring out not just what the tax mix is going to be but also the simplicity of the system, because there's a lot of economic cost to abiding by a very complex tax system.
It is here that we get into questions about whether.... I was encouraged that the budget eliminated some of the boutique tax credits, simply on the basis of simplifying the overall tax system, but I think that's where you end up, over time. The tax system incrementally tends to want to become more complex.
I would echo the comment that a review of the tax system and looking for ways to create more efficiencies to improve the tax mix and make it more efficient would be a very desirable thing.