Hampson Sarah E. et al. found the following results in their study:^[2]Hampson, Sarah E, and Lewis R Goldberg. “A first large cohort study of personality trait stability over the 40 years between elementary school and midlife.” Journal of Personality and Social … Continue reading produced in 2008:

Our analyses are based on data from a relatively large and culturally diverse sample (N = 799) that was first assessed between 1959 and 1967 when the participants were children in Hawaii.

Short-term (1-3 years) test retest reliabilities were lower (.22 -.53) within childhood when personality is developing than within adulthood (.70 -.79) when personality stability may be at its peak.

Stability coefficients across the 40-year interval between the childhood assessment and two measures of adulthood personality were higher for Extraversion (e.g., .29) and Conscientiousness (e.g., .25) than for Openness (e.g., .16), Agreeableness (e.g., .08) and Neuroticism (e.g., .00).

In other words, personality traits extraversion and conscientiousness tend to remain more stable than openness, agreeableness, and most certainly, neuroticism.

Mathew A. Harris et al. noted much the same regarding personality trait stability in children. Stating the following^[3]Harris, Mathew A et al. “Personality stability from age 14 to age 77 years.” Psychology and aging vol. 31,8 (2016): 862-874. doi:10.1037/pag0000133:

Childhood is a period of intense learning and many new experiences, leading to much more frequent small changes in personality, or much more substantial changes over time

Rantanen J. et al. reported much the same when they investigated the stability of the Big Five personality traits in adulthood from age 33 to 42. They also noted in their study ^[4]Rantanen J, Metsäpelto RL, Feldt T, Pulkkinen L, Kokko K. Long-term stability in the Big Five personality traits in adulthood. Scand J Psychol. 2007 Dec;48(6):511-8. doi: … Continue reading that while extraversion, conscientiousness, openness, and agreeableness tend to increase with age, neuroticism tends to decrease with age.

The results showed that the mean-level of Neuroticism decreased whereas the mean-level of Extraversion, Openness to Experience, Agreeableness, and Conscientiousness increased from age 33 to 42.

The Structural Equation Modeling analyses revealed both gender differences and similarities in the rank-order stability of the Big Five: Neuroticism and Extraversion were more stable in men than in women, whereas Openness to Experience, Agreeableness, and Conscientiousness were as stable in men as in women. Stability coefficients for the Big Five personality traits across 9 years were moderate to high, ranging from 0.73 to 0.97 in men and from 0.65 to 0.95 in women.

The highest gender-equal stability was found for Openness to Experience and the lowest for Conscientiousness.

Specht J. et al. ^[5]Specht, Jule et al. “Stability and change of personality across the life course: the impact of age and major life events on mean-level and rank-order stability of the Big Five.” Journal of … Continue reading argued the following:

our analyses show that personality changes throughout the life span, but with more pronounced changes in young and old ages, and that this change is partly attributable to social demands and experiences. 

They also noted the following:

The rank-order stability of Emotional Stability, Extraversion, Openness, and Agreeableness all followed an inverted U-shaped function, reaching a peak between the ages of 40 and 60 and decreasing afterward, whereas Conscientiousness showed a continuously increasing rank-order stability across adulthood.

Furthermore, experiencing a specific major life event also plays a significant influence on existing personality traits.

Brent W. Roberts and Daniel Mroczek performed a study to observe personality trait change in adulthood. ^[6]Roberts, B. W., & Mroczek, D. (2008). Personality Trait Change in Adulthood. Current directions in psychological science, 17(1), 31–35. https://doi.org/10.1111/j.1467-8721.2008.00543. The following is their conclusion.

The results showed that people became more socially dominant over time, especially in young adulthood.

Social vitality showed small increases in adolescence and then small decreases late in life. Although much of the change on agreeableness was positive, the increase was only statistically significant in old age.

People showed little change on conscientiousness in adolescence but then showed remarkable gains in young adulthood and midlife.

Emotional stability showed steady increases through midlife.

Finally, individuals demonstrated gains in openness to experience in adolescence and then equivalent declines in old age. The cumulative amount of personality-trait change across adulthood for -several trait domains exceeded one full standard deviation.

Iris A M Smits et al. published a study to investigate the cohort differences in Big Five personality factors over 25 years^[7]Smits, I. A., Dolan, C. V., Vorst, H. C., Wicherts, J. M., & Timmerman, M. E. (2011). Cohort differences in Big Five personality factors over 25 years. Journal of personality and social … Continue reading

They concluded that esults indicated small linear increases over time in Extraversion, Agreeableness, and Conscientiousness and small linear decreases over time in Neuroticism.

No clear patterns were found on the Openness to Experience factor.

Secondary analyses on students from 1971 to 2007 of females and males of different ages together revealed linear trends comparable to those in the main analyses among young adults between 1982 onward. The results imply that the broad sociocultural context may affect personality factors.