5%..... you're golden.  

One year I helped adjuster find fields and hold tape measure.... came to a really good field (historically) and he had 180.... I thought it was low, so next day, I took the very next 1/1000 acre.... as I could tell exactly where his appraisal came from.... snapped the ears, hand shelled, took to elevator for moisture % and had 280.   Decided to measure rest of field and haul over scale.... 246, dry.  

Most years we have been treated very fairly, and I can't say the adjuster in my example was bad, but for sure, the number he arrived at from the sampled area did not jive with the rest of the field.  

An electrified  hand sheller like someone posted recently doing popcorn should be a valuable tool..... another job for another year!