Why does it take longer to affirm than to reverse?

Appellate stat-master Kirk Jenkins is back in today's DJ offering Why does it take longer to affirm than to reverse? He explains "at the California Supreme Court the time from grant to argument is typically several times as long as the time from argument to decision. By the time the justices reach oral argument, memos have been written and circulated among the chambers, and the justices have at least a tentative idea of which way the court is leaning."

Nevertheless, there's no obvious reason why the lag from grant to argument would be consistently higher depending on whether the court affirms or reverses. If there is a correlation between result and lag time, one might expect reversals to take longer — it would seem to take longer to explain what's wrong with a decision than to agree with it.

But that's not what we found. We calculated lag times for 380 affirmances and 582 reversals in civil cases. If there were no correlation at all between result and lag time, over a large yearly data set one would expect affirmances and reversals to balance out, making lag time averages roughly equal. But for the entire 23-year period, affirmances were argued 491.69 days after review was granted, while reversals were argued 479.13 days after grant.

Reviewing the data year by year, in 12 of the past 23 years, civil affirmances have taken longer to be argued than reversals. And the difference is often substantial. In 2014, civil affirmances took three months longer. In 2012, the margin was approximately six months. In the years when reversals averaged a longer lag time, the margin was never nearly that high. The result is the same if we focus on the lag time from oral argument to decision. Since 1994, civil affirmances have been filed an average of 71.85 days after argument, reversals 70.51 days after. Once again, in 12 of the 23 years in our sample, affirmances took longer to be filed than reversals.