I love Mountain Dew, and when at the store I am faced with a puzzle do I buy the 2 liter, 6-20 fluid ounce bottles, or 12-12 fluid ounce cans. For me this decision is driven by one factor: how I can get more Mountain Dew for less money?

Fortunately,  this puzzle can be solved with reading the label’s net quantity statement. There, however, is a little challenge because the 2 liter is a metric measurement, while the bottles and cans use the U.S. gallon as their basic unit. Fortunately, the labels for all three products gives both the U.S. and metric measurement — so with a little math I can do the price comparison.

However, did Pepsi Co. include both measurements out of the goodness of their heart? Well if you read FDA’s regulations for declaring the net quantity (21 C.F.R. 101.7), the answer appears to be yes.

The regulations specify that the label must include:

(b) (1) Statements of weight shall be in terms of avoirdupois pound and ounce.

(2) Statements of fluid measure shall be in terms of the U.S. gallon of 231 cubic inches and quart, pint, and fluid ounce subdivisions thereof…

The only reference to metric indicates that “an accurate statement of the net quantity of contents in terms of the metric system of weight or measure may also appear…” 21 C.F.R. 101.7(p). In other words, the regulations not just imply, but directly state that metric is optional.

The Regulation Lies.

While the regulations state metric is optional, a separate law explicitly requires a metric declaration. FDA enforces several statutes beyond its namesake the Food, Drug, and Cosmetic Act (FDCA) — one such statute is the Fair Packaging and Labeling Act (FPLA,  let’s hear it for acronym soup). Under FPLA as amended in 1992, the label must declare the net contents in metric too.

So what gives with the regulations? The FDA regulations are far older than the 1992 FPLA amendment. Some aspects of the regulations date back to the 1950s and the metric optional passage dates back to 1967.  32 Fed. Reg. 10729 (July 21, 1967). Amusing, FDA added this language and others because of the original passage of FPLA in 1966.

No Love for the Metric.

When FPLA was first passed, FDA updated the regulations within a year so that the regulations and the statute would align. The same is not true for the amendment to FPLA. It has been 25 years since amendment that made metric mandatory and the regulation still states its optional – why no love?

In 1993, FDA did propose to amend the regulations to require a metric declaration, thereby making the regulation match the law it clarifies. 58 Fed. Reg. 29716 (May 21, 1993). And then nothing happen for almost 10 years until April 22, 2003, when FDA expressed an intent to withdraw the proposed regulation asserting that it was “no longer considered [a] viable candidate[] for final action.” 68 Fed. Reg. 19766. Then over a year later FDA finally withdrew the proposal.  69 Fed. Reg. 68831 (November 26, 2004).

Competing priorities is keeping FDA for solving this gap between the statute and regulations, and it is unlikely that FDA will invest the necessary institutional resources to fix it. For this reason (at least for the net quantity statement), FDA gives no love to the metric system.

This entry was inspired by a recent 99% Invisible podcast (Half Measures), which provides a wonderful story about metric measurement in the United States.