I compiled the historic Delaware yield data for processing peas, green baby limas and sweet corn and developed the two charts below, which show the annual yields and a 5-year running average.  There has been a yield gain of about 4 tons/A for processing sweet corn over the last 45 years and an approximately 0.5 ton/A yield gain for processing peas in the same time period.  For green baby limas, on the other hand, there has been almost no increase in yield.  Improved varieties are undoubtedly a major contributing factor to the yield gains realized for peas and sweet corn.  Meanwhile, as few resources have been devoted to developing improved green baby lima varieties, yields have stagnated.  Hopefully, work at the University of Delaware to develop improved lima bean varieties will help to get that red line moving in an upward direction.