These Class I Prices are calculated by adding applicable Class I differentials (for varying locations throughout the country) to advanced pricing factors for the month in question. In the following example, Class I prices for Dec 2009 for Cook County, Illinois are calculated using the appropriate Class I differential and Advanced values for Dec 2009 released the previous month on Nov 20, 2009
The advanced prices calculated in the section use biweekly average U.S. NASS survey prices. These biweekly average prices are calculated by a weighted average.
These biweekly average prices are as follows:
| AA Butter | 1.3532 |
| Cheddar Cheese | 1.5113 |
| Dry Whey | 0.3452 |
| Nonfat Dry Milk | 1.1147 |
= (Higher of advanced Class III or Class IV skim milk pricing factors + applicable class1 differential)
= ($9.5 + $1.80)
= 11.3
So, the Class I Skim Milk Price for Dec 2009 is 9.5
= (Advanced Butterfat Pricing Factor + applicable class1 differential/100)
= ($1.4796 + $0.0180)
= 1.4976
So, the Class I Butterfat Price for Dec 2009 is 11.3
= (Class I Skim Milk Price x 0.965) + (Class I Butterfat Price x 3.5)
= ($11.3×0.965) + ($1.4976×3.5)
= 16.1461
So, the Class I Price for Dec 2009 for Cook County, IL is 16.1461