Stability of Personality and Formation As an economist I'm interested in what shapes personality and Indeed whether or not personality/traits change over time. For example, does personality change when placed in a high pressure environment, let's say a demanding job. Or does a demanding job attract those with a certain personality. I would have thought it would be a combination of the two. I presume significant life events would shape personality to some degree. Furthermore, is personality something that's formed in childhood or is it more biological. Is our personality always evolving? I apologize if this seems trivial! Economists are not renowned for their knowledge of Psychology.
Actually some if not all of your question can be answered fairly succinctly by quoting from a fairly recent meta analysis cited in the Wikipedia page on the topic:


  The longitudinal stability of personality is low in childhood but increases substantially into adulthood. Theoretical explanations for this trend differ in the emphasis placed on intrinsic maturation and socializing influences. To what extent does the increasing stability of personality result from the continuity and crystallization of genetically influenced individual differences, and to what extent does the increasing stability of life experiences explain increases in personality trait stability? Behavioral genetic studies, which decompose longitudinal stability into sources associated with genetic and environmental variation, can help to address this question. We aggregated effect sizes from 24 longitudinal behavioral genetic studies containing information on a total of 21,057 sibling pairs from 6 types that varied in terms of genetic relatedness and ranged in age from infancy to old age. A combination of linear and nonlinear meta-analytic regression models were used to evaluate age trends in levels of heritability and environmentality, stabilities of genetic and environmental effects, and the contributions of genetic and environmental effects to overall phenotypic stability. Both the genetic and environmental influences on personality increase in stability with age. The contribution of genetic effects to phenotypic stability is moderate in magnitude and relatively constant with age, in part because of small-to-moderate decreases in the heritability of personality over child development that offset increases in genetic stability. In contrast, the contribution of environmental effects to phenotypic stability increases from near zero in early childhood to moderate in adulthood. The life-span trend of increasing phenotypic stability, therefore, predominantly results from environmental mechanisms.


(emphasis mine) And since the abstract is somewhat devoid of figures... later in the article the contributions are quantified:


  Heritability tends to be high and accounts for the large majority of variance in infancy. Heritability declines substantially in early childhood and somewhat more slowly thereafter, resulting in roughly 40% of variance in personality attributable to genetic influences throughout adulthood. Environmentality displays the opposite pattern. Corrected for measurement error, environmentality shows a similar upward trajectory with a peak of accounting for over 40% of variance in personality. [...]  By midlife, genetic and environmental effects were found to contribute almost equally to phenotypic stability. 


That half-and-half figure may be somewhat easy to misinterpret though. That's because environment doesn't necessarily mean present environment, i.e. someone's personality may be substantially affected by past events that are not easy to "undo" (counter-effect). More recent research has put the combined figure of stable influences affecting personality (e.g. genes, past environment, considered as a whole) to 83%. That sounds fairly consistent with voluntary attempts at changing one's personality having relatively small effect.