It is not only shorter than other vowels (Lehiste, Teras, Help, Lippus, Meister, Pajusalu, Viitso 2005), but it is also opposed to full vowels from the point of view of accentuation--strong formatives cannot contain only reduced vowels.
It is easy to notice the similarity between this system and the Mari accentuation that operates with weak formatives, strong formatives and lan and la formatives that distribute the stress between two syllables.
In some dialect there are formatives that draw the stress to themselves (Geisler 2005:157-162).
It is based on the contrast of weak and strong formatives and demonstrates correlation between the stress and quality of vowels (the accentuation behavior of the reduced vowel e and full vowels is crucially different).
13) This fact is very important because it gives us a possibility to avoid circulus vitiosus, when the accentuation rule is based on splitting a word into formatives, but the list of formatives is compiled on the basis of accentuation characteristics.
22) In Standard Mari the word 'bad' is sukso and it consists of two formatives (root plus harmonic): suks+o.
However, usually the etymology of adverbs with this formative is not transparent on the synchronic level, and thus we cannot use the features of the source word as a reliable criterion for distinguishing between the weak and strong ge formatives.
What I suggest instead is formulating the rule of Mari stress in terms of morphophonology using a notion of formative as a unit of morphophonological representation.
From the point of view of accentuation every formative can be qualified as weak or strong (the qualifying principles are discussed in section 4.
If there are several vowels in a strong formative, the stress is placed on the rightmost full vowel (7) in the formative.
How one can define whether a formative is weak or strong?
The same formative is part of the following suffixes (traditionally described as derivational): demo/demo/deme, (10) lo/lo/le, so/so/se (derive adjectives from nouns), zo/zo/ze, co/co/ce (derive nouns from nouns), and eske (in this suffix the final vowel is always e because it is preceded by another e that unambiguously defines the harmonic variant).