Loss aversion — Kahneman & Tversky (1979) prospect theory; REPLICATION-FLAGGED: Gal & Rucker (2018) challenged universal 2:1 claim; Walasek/Mullett/Stewart meta-analytic re-examinations find coefficient ≈1.3 (or near 1 under symmetric conditions); Kahneman conceded "not a law of human nature"

Claim: Loss aversion is the finding that losses loom larger than equivalent gains in subjective experience. For new-site owners, a slow start is framed as a loss relative to the anchored vendor expectation, amplifying the urge to abandon or over-correct.

Source: Kahneman, D., & Tversky, A. (1979). "Prospect Theory: An Analysis of Decision under Risk." Econometrica 47(2):263–291.

Confidence: Industry-consensus that loss aversion EXISTS as a direction. Directional on MAGNITUDE.

The widely-cited "losses loom roughly 2× larger than gains" coefficient is no longer accepted as a universal value:

• Gal & Rucker (2018) challenged the universal 2:1 claim and argued the field had over-extended the original finding.
• Meta-analytic re-examinations by Walasek, Mullett & Stewart find the coefficient highly moderated and far lower (≈1.3), or near 1 under symmetric, unordered conditions.
• Kahneman himself conceded the effect is "not a law of human nature that you have to find it in every context."

Caveat: Loss aversion is one of the two replication-flagged mechanisms in the brief (the other is Illusion of control — Langer (1975); REPLICATION-FLAGGED: classic Study 2 failed to replicate in Kühberger et al. (1995, four experiments, none successful)). Cite the direction confidently; do not cite the 2:1 coefficient as settled. How loss aversion scales to the "slow launch" framing specifically is unmodeled — a known gap.