Descriptive Statistics and Preliminary Analyses
Supplemental material
Table S1 summarizes descriptive statistics by society. Columns 2–9 present the means and standard deviations of the individual-level variables, including SWB and future optimism at both time points. Column 10 lists the proportion of male respondents, while Column 11-12 reports the mean and standard deviation of baseline age. Columns 13 and 14 provide the societal-level indicators, Flexibility–Monumentalism, and the HDI. Columns 15 and 16 show the included samples and missing cases for each society and region.
To ensure that the factor structure derived from the overall sample was appropriately represented within each society or region, we conducted a Procrustes rotation (
van de Vijver & Leung, 2021) and calculated Tucker’s phi congruence coefficients (
Tucker, 1951) to assess factorial agreement across countries and regions. The results showed high congruence. In particular, SWB both at Time 1 and Time 2 had an average Tucker’s phi of 0.997 (see
Supplemental Material Table S3). Tucker’s phi values exceeded the recommended threshold of 0.950, indicating a good congruence across countries and regions (
Lorenzo-Seva & Ten Berge, 2006).
To assess the need for multilevel modeling, we first estimated unconditional models with SWB and future optimism at Time 2 as outcomes. The resulting intraclass correlation coefficients (ICC) were 0.126 and 0.121, respectively, both exceeding the 0.059 guideline suggested by
Cohen (2013). These values indicate that a meaningful share of the variance lies between societies, warranting the use of multilevel models.
Main Model Results
Table 1 reports the estimates from the primary multilevel models. Future optimism at Time 1 was not significantly associated with SWB at Time 2 (
b = 0.036,
p > .05). In contrast, SWB at Time 1 was positively related to future optimism at Time 2 (
b = 0.291,
p < .001), consistent with Hypothesis 1b. Both constructs also showed considerable temporal stability: SWB at Time 1 was strongly associated with SWB at Time 2 (
b = 0.576,
p < .001), and future optimism at Time 1 was closely related to future optimism at Time 2 (
b = 0.307,
p < .001).
Among the controls, gender and age demonstrated systematic associations. Males reported higher levels of SWB (b = 0.027, p < .001) while there was no significant association between gender and future optimism (b = −0.015, p > .05). Older respondents tended to report greater SWB (b = 0.002, p < .001) but lower future optimism (b = −0.003, p < .001).
Table 2 summarizes the results from the full multilevel models, which include both individual- and societal-level variables as well as cross-level interactions. At the individual level, future optimism at Time 1 was positively related to SWB at Time 2 (
b = 0.036,
p < .05), and SWB at Time 1 was positively associated with future optimism at Time 2 (
b = 0.290,
p < .001). Both outcomes also demonstrated high temporal stability (SWB:
b = 0.576,
p < .001; future optimism:
b = 0.307,
p < .001). Gender and age showed consistent patterns, with males reporting higher SWB, while no gender difference in future optimism, and older individuals showed higher SWB but lower optimism. Considering gender diversity, respondents identifying as other genders were included in the additional analysis. As shown in
Table S4, they reported slightly lower SWB (not statistically significant,
p > .05) and significantly lower future optimism (
p < .001) compared with males and females.
At the societal level, FLX-MON was not significantly related to both SWB (
b = −0.133,
p > .05) and future optimism (
b = −0.563,
p > .05). In contrast, the HDI was positively associated with SWB (
b = 1.224,
p < .01) and was positively correlated with future optimism (
b = 1.312,
p < .01). The models also incorporated cross-level interactions to test moderation by FLX-MON. The interaction between future optimism at Time 1 and FLX-MON was significant for SWB at Time 2 (
b = 0.215,
p < .01), suggesting that optimism had stronger implications for well-being in more flexible societies, which is consistent with Hypothesis 2a. Likewise, the interaction between SWB at Time 1 and FLX-MON was significant for future optimism at Time 2 (
b = 0.549,
p < .001), supporting Hypothesis 2b. These findings highlight the role of cultural orientation in shaping the reciprocal links between future optimism and SWB. Robustness checks, reported in
Tables S5–S7, indicate that the findings remain stable when analyses are conducted without sampling weights and when additional cultural dimensions are included as control variables.
To test effect sizes, we evaluated the magnitude of differences between individuals at the extremes of future optimism and SWB. Following
Geerling and Diener (2020), we compared respondents scoring the highest on future optimism (10 points;
N = 38,101) with those scoring the lowest (0 points;
N = 1,790). The future optimism difference in SWB at Time 2 was large (
d = 1.568, 95% CI = [1.520, 1.617]) (
Cohen, 2013;
Geerling & Diener, 2020). Likewise, respondents scoring the highest on SWB (10 points;
N = 3,496) and those scoring the lowest (0 points;
N = 66) were compared. The difference of SWB in future optimism at Time 2 was large (
d = 2.745, 95% CI = [2.493, 2.997]) (
Cohen, 2013;
Geerling & Diener, 2020).
Because the number of participants scoring 0 on SWB at Time 1 was small (
N = 66), we also considered broader low-SWB groups (0-1 and 0–2). Specifically, respondents scoring the highest on SWB at Time 1 (10 points;
N = 3,496) were compared with those scoring 0 to 1 points (
N = 303). The difference in future optimism at Time 2 was large (d = 2.538, 95% CI = [2.407, 2.668]) (
Cohen, 2013;
Geerling & Diener, 2020). A similarly large effect size was observed when comparing the high-SWB group with the broader low-SWB group (0 to 2 points;
N = 980), again yielding a large difference in future optimism at Time 2 (d = 2.274, 95% CI = [2.189, 2.359]).
To further probe the significant moderation by Flexibility–Monumentalism, we conducted simple slope analyses.
Figure 2 illustrates the conditional effects, with FLX-MON plotted at the upper quartile (flexibility) and the lower quartile (monumentalism). For comparability, the upper and lower quartiles of baseline future optimism and SWB were used to illustrate the range of the sample distribution. The left panel shows that the association between future optimism at Time 1 and SWB at Time 2 was stronger in more flexible societies, whereas the relationship was nearly flat in more monumental societies. The right panel indicates a similar pattern for the reverse pathway: SWB at Time 1 was more strongly linked to future optimism at Time 2 in flexible societies, while the slope was weaker under monumentalism. These results reinforce the cultural contingency of the reciprocal association between optimism and well-being and provide robust support for Hypotheses 2a and 2b.