WE PROPOSE TO DETERMINE STAR FORMATION HISTORIES OF GALAXIES SINCE A REDSHIFT OF 5. IN PARTICULAR, WE WILL MEASURE THE FRACTION OF GALAXIES WHICH EXPERIENCE SIGNIFICANTLY ELEVATED AND DEPRESSED STAR-FORMATION ACTIVITY WITH RESPECT TO THE COSMIC AVERAGE, AND QUANTIFY THE AMOUNT OF TIME GALAXIES SPEND IN SUCH STATES. WE WILL DO THIS USING OUR NEW GALAXY SPECTRAL MODELS WHICH ARE BASED ON A COMBINATION OF STAR-FORMATION AND CHEMICAL ENRICHMENT HISTORIES FROM HIERARCHICAL SIMULATIONS OF GALAXY FORMATION. WE PROPOSE TO USE THESE MODELS TO FIT AN EXTREMELY LARGE DATA SET OF 105,000 GALAXIES OVER 0.2