Are USA marathoners worse than they were 25 years ago?

Are the US Marathoners better than they were 25 years ago or is it just the shoe tech and fueling that has made everyone faster? Rod DeHaven’s 2:11:40 in Chicago in 2002 was closer to the front than Clayton young 24 years later. Were Ryan Hall in London 2008 and Deena Kastor white wales? 0:00 The US marathon gap 1:40 Historical performance 2:52 Competitive challenges 4:51 Galen Rupp's career