Merging Areas In Timber Mart South Data
For over twenty years, Timber Mart-South (TMS) has been distributing prices of various wood products from Southern forests. These long-term price series have been a critical resource for research into timber price and supply trends in the southern United States. Such analyses rely on consistent temporal and spatial reporting units, but these units have not always been consistent for many TMS reporting unit series. In the beginning of 1988 the reporting frequency changed from monthly to quarterly, a change readily addressed through a variety of established statistical techniques. A more significant statistical challenge is Timber Mart-South's change in 1992 from (typically) three reporting regions per state to two. We developed a conversion technique to address this change in reporting areas, permitting longitudinal analyses of the current two regions per state but extending back to the beginning of Timber Mart-South's reports in 1976. We report conversion factors for every state's regions, verify the statistical nature of all time series created using them, and report tests of seamlessness. We find that our technique enables the creation of new, seamless series for pine sawtimber stumpage and delivered sawlogs, and pine and hardwood pulpwood stumpage and delivered logs. In only a few cases were we able to identify remaining regime shifts in the time-series of quarterly prices that corresponded with the 1992 boundary reconfigurations. However, these statistically significant shifts may not be related to the boundary reconfigurations.