According to data from four of the 10 federal milk marketing orders, bulk tank somatic cell counts have been on a downward trend continuously since 2007.
A report by the U.S. Department of Agriculture indicates that nearly 50 percent of the bulk tank sample readings were at between 200,000 and 399,000 somatic cells per milliliter in 2011 - the latest year for which the data has been released.
Including the milk shipments with a count lower than 200,000 during the monitored months, the bulk tank somatic cell count was below 400,000 on 80 percent of the milk shipments, representing 92.7 percent of the milk.
But only 53.6 percent of the 29,937 producers in the four milk market orders shipped milk at below 400,000 somatic cells for the entire year.
At the other end, or undesirable, end of the scale, less than one percent of the milk and two percent of the sampled shipments did not meet the inter-state Pasteurized Milk Ordinance's (PMO) limit of 750,000 somatic cells per milliliter.
All but 2,305 of the 29,937 producers shipped milk at below 750,000 somatic cells during each of the monitored months.
During its next meeting, the National Conference on Interstate Milk Statements could decide to lower the PMO limit from 750,000 to 400,000.
That would put it in compliance with the European Union's official standard for any milk used for manufactured products imported by its member countries.
In the United States, many processors who export dairy products to Europe have essentially put a 400,000 somatic cell limit in place on milk they accept from shippers so they don't have to segregate milk based on it having a cell count above or below 400,000.
On a milk solids basis, up to 13 percent of U.S. milk production is exported. However, only a small portion of those exports go to Europe.