According to the Southern Pine Inspection Bureau Notices page and Costal Contractor Online, the Southern Pine lumber industry is dealing with concerns that design values for visually graded southern pine lumber may need to be reduced.  This need is based upon private testing and industry testing, which has reportedly indicated that a general downward trend in stiffness and bending stress values exist when data over a period of time is evaluated for No.2 2x4 studs.  There is concern that design values may need to be reduced as much as 25%-30% for No. 2 2x4 stud; however, caution is emphasized this concern is only for 2x4 lumber at this time.  Under discussion is whether this affects other dimensional lumber, and if so, to what extent.  Currently there is discussion among the governing agencies about the need for modification of design values, but also in the procedures used to develop these values.  Design professionals are cautioned to stay apprised of the current discussion and design recommendations.  For the best and most current information, check the Southern Pine Inspection Bureau (SPIB) for recommendations and announcements.

Additional reading for more depth on this subject:

Southern Pine Inspection Bureau Notices

Forest Business Network.

Costal Contractor Online