Kaiser, one of the nation’s largest health care providers, has proposed a two-tiered wage and benefits system that would give newer employees lower pay and fewer health protections. The unions want Kaiser to abandon that plan. They also want 4% raises for each the next three years and a commitment to hire more nurses to relieve staffing shortages. Kaiser has offered 1% a year, with additional lump sums, and says it must reduce labor costs to remain competitive.