According to Packard, nearly 90% of compound nouns have a nominal formant on the right. The right-hand rule suggests that the default position of the head of a nominal is on the right-hand side of a disyllabic compound. This principle also illustrates the modifying nature of the morpheme on the left.
For example, in the compound words ni´u-n˘ai (牛奶/ cow milk) and y´ang-n˘ai (羊奶/ sheep milk), the morphemes on the right reveal the property of nouns, and the ones on the left indicate the producer of the milk.
Reference: Chinese: a linguistic introduction by Chao Fen Sun