In the EU the average quantity system is permitted. Below is an outline
from a UK Trading Standards site.
> What is the Average System?
>
> The average system controls the weight or measure of most pre-packed goods. Packages
>must be marked with the weight
> or volume of the contents. Packers and importers must ensure that their packages
>comply with the following rules, known as
> the �3 Packers Rules�:-
>
> 1. The contents of packages must not, on average, be less than the amount marked
>on the label (known as the
> nominal quantity).
>
> 2. Not more than one package in forty may contain less than the nominal quantity
>by more than an amount called
> the Tolerable Negative Error (TNE). This varies according to the nominal
>quantity, eg 9g on a 250g pack. Such
> packages are called �non-standard�.
>
> 3. No packages may contain less than the nominal quantity by more than twice the
>TNE. These are called
> �inadequate packages�.
>
> The system applies to all goods listed in the Weights and Measures (Packaged Goods)
>Regulations 1986 in packages made
> up in a pre-determined constant quantity. Packs made up otherwise than in a
>pre-determined constant quantity are known
> as catchweight and are outside the average system. Such packs continue to be covered
>by the traditional minimum system
> and must contain at least the stated quantity.
>
> Packages of goods not included in the average system may be voluntarily brought into
>it if they are within the range 5g/5ml
> to 10kg/10l and are �e� marked. This allows packers of products not included in the
>Regulations to use the average system
> of control. The �e� mark also acts as a metrological passport for packaged goods
>that pass between EC countries, allowing
> such items free passage without any further quantity checks being necessary.
>
> There is no requirement to pack to the average system and it is quite permissible to
>continue working to the �minimum
> system�. However, packers of average system products who choose to pack on a minimum
>system basis either make up
> every package on prescribed equipment, or check samples and keep records. In
>general, less checking is needed when
> packages are systematically overpacked. This can be an advantage where the goods are
>relatively inexpensive.
>
>
