John T. Manhire, Jr. (Attorney Advisor, National Taxpayer Advocate) has posted Is Chevron Dead in the U.S. Tax Court (and Does It Matter)?: A Brief Study of Validation Rates from 1993 to 2010 on SSRN. Here is the abstract:

For over twenty-five years, the Chevron Doctrine stood firm as the most deferential standard in administrative law. The Doctrine holds that politicians, not judges, should make policy judgments. Many thought Chevron reduced variations in the judiciary by upholding all reasonable agency interpretations of ambiguous terms in a statute. However, some scholars believe Chevron’s high standard of judicial deference to agency actions is on the wane, and attribute this attenuation to a de facto return to the less deferential Skidmore standard. Ann Graham went so far as to declare a traditional Chevron analysis “dead – or at least critically wounded” in the U.S. Supreme Court. Bryan Camp is more visceral, stating, “Everyone starts with Chevron. What a crock.” Observations that Chevron is no longer the great pillar of deference and consistency it once was prompted this brief empirical study to determine if Chevron is “dead or critically wounded” with the U.S. Tax Court.

I study forty-four Tax Court cases from 1993 to 2010, excluding memorandum and summary opinions, where the majority either validated or overturned an IRS regulation using a Chevron analysis. I categorize the data and then analyze it in two-year groups. My hypothesis is that significantly lower validation rates under Chevron in recent years might indicate that the Tax Court is becoming less deferential to IRS regulations.

The data indicates that the Tax Court’s validation rates are at an 18-year low. I proffer that this historic low is arguably significant in that it is at least a 320 percent increase in the maximum variance between previous periods. On the other hand, an aggregate analysis of the same data suggests that the Tax Court is no less deferential than other federal courts in previous years. This could be attributable to the Tax Court’s recent cases focusing on the same statutes of limitation issue for innocent spouse claims. I conclude this study with a recent review of Chevron and Skidmore rates from other federal courts since 1984 to determine if the question of whether Chevron is dead has any practical implications, or is purely academic.