A 2017 paper written by five economists (Andreoni et al.) finds that
Time preferences have been correlated with a range of life outcomes, yet little is known about their early development. We conduct a field experiment to elicit time preferences of nearly 1,000 children ages 3-12, who make several intertemporal decisions. To shed light on how such primitives form, we explore various channels that might affect time preferences, from background characteristics to the causal impact of an early schooling program that we developed and operated. Our results suggest that time preferences evolve substantially during this period, with younger children displaying more impatience than older children. We also find a strong association with race: black children, relative to white or Hispanic children, are more impatient. Interestingly, parents of black children are also much more impatient than parents of white and Hispanic children. Finally, assignment to different schooling opportunities is not significantly associated with child time preferences.
Technically the findings only apply to African-American children and parents (nothing is said about childless adults) but I think the question raised should obviously more general. Actually, the authors themselves phrase it later as:
As a whole, it appears that black households exhibit more impatience, which is already apparent in young children.
Is this race-difference in patience consistent with other studies? I'm aware of much discussed race-IQ question in the US, but I wasn't aware of any time-preference/patience vs race research until I saw this paper.
As a footnotes I will note here that socio-economic status correlates with [im]patience... in some studies:
Related work has found that children from families with higher socio-economic status (SES) or higher quality of early childhood home environment tend to exhibit more patient preferences (Deckers et al., 2013; Shildbert-Horisch et al., 2014; Falk and Kosse, 2016). And, Castillo et al. (2011) found that black adolescents tend to be more impatient than non-black adolescents.
but Andreoni et al. says it doesn't explain the race difference they observed in their sample (all of which was basically low SES):
There are no statistically significant differences in child age and gender by race. Black children are similar to Hispanic children on the basis of household income, and look similar to white children on the basis of mother’s educational attainment. Hence, differences in SES may not explain our results.
Also, they also point to another study Castillo et al. (2011) corroborating their race difference in the patience of adolescents... but that study also found a gender-based difference... which Andreoni et al. found was not robust in their own sample.
So... all these contradictory findings in this area of research do raise the question whether two (concordant) studies establish a fact.