Baseline 2012 data on the workforce were reported (OCCD & OCCRP, 2014) with follow up reports one year (OCCD & OCCRP, 2015) and two years (OCCD & OCCRP, 2016) after the baseline. Working together, OCCD, ELD, and the Oregon Child Care Research Partnership at Oregon State University (OSU) have analyzed the data for a fourth year, 2015. As with the previous reports, this brief answers questions that partners have determined to be most critical for supporting decision makers as Oregon works to improve outcomes for its youngest children. This brief is the fourth of what will be annual reports on the workforce. In this fourth report, we compare findings with the baseline. This comparison provides a measure of the impact of early childhood investments on the workforce by viewing changes in important workforce characteristics. (author abstract)