The benefits of reducing current tax liabilities through tax loss harvesting are widely acknowledged - so much, that the IRS developed the 30-day "wash sale" rules to prevent taxpayers from abusing the strategy. Yet less widely understood is that there's one crucial caveat to tax loss harvesting - that taking advantage of the loss also reduces the cost basis of the investment, potentially exposing the taxpayer to a gain in the future that can wipe out some, most, or all of the tax benefit, and in the extreme with today's four capital gains tax brackets actually drive up future tax rates and leave the investor worse off than having done nothing at all.
Notwithstanding these issues, many investors and advisors continue to overstate the benefits of tax loss harvesting, and now "robo-advisor" Wealthfront is doing so as well, with its "Tax-Loss Harvesting White Paper" that purports Wealthfront can increase an investor's wealth by an extra 1%/year, annualized, indefinitely, through its daily tax loss harvesting strategy. Unfortunately, though, the reality is that in a review of its strategy, Wealthfront - like so many others - is confusing tax savings with tax deferral, and in the process may be drastically overstating its benefits by a factor of 10:1, and for its typical investor the true annual benefit may be a mere 1/25th of what their "white paper" claims purport.
Again, this is not to say that tax-loss harvesting is useless, and in reality while many advisors have been automating tax-loss harvesting just like the robo-advisors for almost a decade, Wealthfront's particular tools to implement loss harvesting are unique, especially in how it is able to quasi-pool investor assets to drive the transaction costs down to nothing for its clients (facilitating tax loss harvesting at very small thresholds on a nearly continuous basis!). Nonetheless, the flaws of the Wealthfront tax-loss harvesting white paper also provide a clear example of the problems with trying to come up with a generalized algorithm for an individual's specific and unique tax circumstances, and overall provides an unfortunate case study in how not to calculate tax alpha and try to apply its benefits for a wide range of clientele.