As the dividend/price ratio is negatively related to fluctuations in prices, he model predicts a negative relation between this variable and the middle-aged-to-young ratio.
In a recent CEPR Discussion Paper (Favero et al. 2010), we take the Geanakopoulos et al. model to the data via the conjecture that fluctuations in the middle-aged-to-young ratio could capture a slowly evolving mean in the dividend price ratio within the dynamic dividend growth model.
The best adult-young ratio to induce song learning from adults appears to be 1∶1 [16], [16].
Beyond the mere presence or absence of adults, the adult-young ratio (i.e. the relative proportion of adults in a group) appears to be an important factor for social development, both in animals and in humans.
Although the presence of adults sometimes seems to induce closer associations between young (e.g. cowbirds [11], domestic horses [14]), other studies [15], [16], including this one, specify that associations between young could depend on the adult-young ratio: low proportions of adults in social groups induce more social segregation between young and adults than do high proportion of adults.
We found striking variations of aggression rates and spatial relationships related to the adult-young ratio: the lower this ratio, the more the young were aggressive, the more young and adults segregated and the tighter the young bonded to other young.
Here, we hypothesized that aggression rates and social cohesion were correlated to adult-young ratios.
Here, we observed naturally-formed groups with various adult-young ratios and hypothesized that adult-young ratios would influence aggression rates and social cohesion of young Przewalski horses, Equus f. przewalskii.
Only long-term experimental manipulations of adult-young ratios in groups could fill this gap in our understanding.
This is the first study demonstrating a correlation between adult-young ratios and aggression rates and social cohesion of young individuals in a naturalistic setting.
The adult-young ratios observed in this Przewalski horse population are similar to those observed in feral horse populations (e.g. from 0.50 to 1.30 [26], [26]).
