Data Snooping and Market-Timing Rule Performance

We reassess the performance of market-timing rules when controlling for data-snooping biases. For the first time, a comprehensive set of simple and complex market-timing rules is examined and tested for statistical significance, using the White (2000) "Reality Check," the Hansen (2005) SPA test, as well as their stepwise extensions by Romano and Wolf (2005) and Hsu, Hsu, and Kuan (2010). Even though individual market-timing rules significantly outperform a buy-and-hold strategy at both daily and monthly frequencies when considered in isolation, their outperformance, generally, does not remain significant after correcting for data snooping. Relative to the alternative of investing in the risk-free rate, however, we find significant outperformance of the best rules, even after data-snooping adjustment, when testing at a monthly timing frequency. (JEL: G11, G14) Copyright The Author 2011. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: [email protected], Oxford University Press.

A spatially resolved brain region- and cell type-specific isoform atlas of the postnatal mouse brain

Splicing varies across brain regions, but the single-cell resolution of regional variation is unclear. We present a single-cell investigation of differential isoform expression (DIE) between brain regions using single-cell long-read sequencing in mouse hippocampus and prefrontal cortex in 45 cell types at postnatal day 7 (www.isoformAtlas.com). Isoform tests for DIE show better performance than exon tests. We detect hundreds of DIE events traceable to cell types, often corresponding to functionally distinct protein isoforms. Mostly, one cell type is responsible for brain-region specific DIE. However, for fewer genes, multiple cell types influence DIE. Thus, regional identity can, although rarely, override cell-type specificity. Cell types indigenous to one anatomic structure display distinctive DIE, e.g. the choroid plexus epithelium manifests distinct transcription-start-site usage. Spatial transcriptomics and long-read sequencing yield a spatially resolved splicing map. Our methods quantify isoform expression with cell-type and spatial resolution and it contributes to further our understanding of how the brain integrates molecular and cellular complexity