The IA state data shows clearly show as machine width increases field efficiency decreases.  Talk to the guys running 48R30 planters and they will tell you they did not double their acres planted per day/hr coming from 24R30, they end up closer to 80-85% more acres per day, not 100%.  Guys that went from 12R30 to 24R30 said the same thing about 80-85% more per day and not doubling capacity.  Sprayers are worse yet because they only spend 35% of the time spraying and a 176' boom might cover 60% more acres than a 80ft in a day.

The reality is larger machines typically take longer to switch from transport to field and field to transport than the smalller machines; some may not even need to be folded/disconnected for transport.  This takes time.  Next, most every field has headlands so it takes the about the same time to travel the perimeter of the field regardless of implement size, the difference being the larger implement covers more acres in the same time which makes the main portion of the field smaller.  At the end of every field you end up with the check rows that againg take the same time to cover with a larger machine.  So now considering more time to switch from transport to field, same time spend on headlands, same time for check row, and less time in main portion of the field because it is smaller you find that the efficiency gain in the main portion of the field does not offset the 

I used your example of 30 and 40 and added 35 and 45 in both corner 80s and middle 80s assuming 33' ROW.  Assumptions were headland harvest at 4mph, headland turns at 1.5mph (allows for backup, cut in, and turn around), main field harvest at 4.5mph and main field turns at 4.5mph.  Turns are semi circle + 5ft lead out and 5ft lead in.  Total field time is HL Total + MF Total.  HL Total is HL Harvest + HT total turn while MF Total is MF Harvest + MF Total Turn + Dead Head Time.  Perfect tiem is field acres *43560 / hw / 6.6 ft/s and Harvest efficiency is perfect time / Total Field Time.  As you can see Harvest Efficiency decreases as header width increases.

With that IA state says field efficiency decreases as implement width increases, farmer testimonial states field efficiency decreases ans implement width increass, and calculations show field efficiency decreases as implement width increases.  You are wrong, which is understandable since you forgot as machine width increases, headlands/opening a field becomes a larger percentage of the time spent in the field and consequently the main portion of the field becomes a smaller percentage of the time.  The less turns is important, but the turns are also bigger which means turn time is very similar in the main part of the field.

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