 34. Personality and Subjective Well‑Being 731
mortality over and above more objective 
measures (e.g., Ganz, Lee, & Siau, 1991; 
Rumsfeld et al., 1999), and studies that have 
investigated the discrepancies between self- 
and doctor-  rated health have found evidence 
that it may be the doctors’ judgments that 
are wrong (e.g., Nelson et al., 1983).
The examples we just described show that 
associations that appear to be very small can 
actually be quite large when alternative ef -
fect size indices are examined or when ap -
propriate measures of predictor variables are 
used. Unfortunately, the opposite can also 
be true. Effects that have been considered 
very large may not be so large when exam -
ined closely. We have argued that this is the 
case with variables related to the existence 
of social relationships (Lucas & Dyrenforth, 
2005, 2006). When predictors of SWB are 
compared, variables such as the existence of 
strong social relationships are presented as 
if they are the strongest correlates to emerge 
from the literature (e.g., Argyle, 2001). How -
ever, reviews of this literature often focus on 
satisfaction with relationships, or the extent 
to which people value relationships, rather 
than on the existence of relationships them -
selves. If these more objective measures are 
evaluated, the correlations are similar to, 
and perhaps even smaller than, the associa -
tion with income.
For example, Lucas and Dyrenforth 
(2006) reviewed the literature on the as -
sociations between SWB and the number 
of friends a person has, whether an indi -
vidual has a close friend to whom he or she 
can talk, the amount of time that a person 
spends with friends, and the amount of time 
that a person spends with family members. 
Existing meta-  analyses (e.g., Okun et al., 
1984; Pinquart & Sörensen, 2000), along 
with new analyses of data from nationally 
representative surveys, showed that cor -
relations with these variables tended to be 
around .15 and very rarely exceeded .20. 
Even marital status, which has often been 
held up as one of the most important demo -
graphic predictors, only correlates .14 with 
measures of SWB (Haring-  Hidore, Stock, 
Okun, & Witter, 1985). Thus, at least when 
relatively objective measures are assessed, 
these associations are smaller than the effect 
of income or health (e.g., Hudson, Lucas, & 
Donnellan, 2020).We acknowledge that the same concerns 
about the interpretation of effect sizes that 
we raised for income and health may also 
apply to correlations with social relation -
ship variables. A very small correlation 
may be meaningful, and simple count- and 
frequency-  based measures of social relation -
ships may not adequately capture the quality 
of these relationships. Furthermore, social 
relationships, including marriage, predict a 
wide variety of outcomes that include risk 
for mental illness, poor physical health, and 
even death (e.g., Berkman & Syme, 1979; 
House, Landis, & Umberson, 1988; House, 
Robbins, & Metzner, 1982). Thus, the ro -
bustness of these effects across domains may 
be important, even if the individual effects 
are quite small. However, because it is dif -
ficult to say whether an individual effect size 
is practically important, researchers must be 
careful to compare apples to apples when 
drawing conclusions about the relative im -
portance of different life circumstances.
The three domains we have reviewed pro -
vide just a small sample of effects from the 
large body of literature linking SWB to de -
mographic characteristics and other external 
life circumstances. Considerable research 
has also investigated factors such as age, 
gender, education, employment status, eth -
nicity, and religion. A more detailed review 
is beyond the scope of this chapter, though 
we refer the reader to other sources, includ -
ing Argyle (1999, 2001) and one of our pre -
vious reviews (Diener et al., 2018) for more 
detailed coverage. Our goal here is to point 
out that although effect sizes have often been 
found to be quite small, these effects must be 
interpreted carefully. The types of character -
istics reviewed in this section do not account 
for much variance in SWB scores, but this 
lack of variance does not necessarily mean 
that they are unimportant. Individuals who 
become unemployed, acquire a disability, or 
lose contact with a close friend may, in fact, 
experience lasting changes as a consequence 
of these losses. Thus, SWB may be more 
strongly influenced by life circumstances 
than has generally been assumed.
Heritability of  SWB
The second piece of evidence for personality 
effects comes from behavioral genetics stud -