{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,11]],"date-time":"2026-10-11T16:46:03Z","timestamp":1791737163913,"version":"4.3.4"},"posted":{"date-parts":[[2026]]},"group-title":"SSRN","reference-count":19,"publisher":"Elsevier BV","license":[{"start":{"date-parts":[[2026,1,1]],"date-time":"2026-01-01T00:00:00Z","timestamp":1767225600000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/www.uspto.gov\/ip-policy\/copyright-policy\/copyright-basics"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:p>This paper studies robust consumption and portfolio choice under ambiguity regarding diffusion, disaster jump, and business-cycle transition risks in complete and incomplete markets. With CRRA preferences, we derive semi-analytical optimal policies and quantify welfare costs. Market completeness changes how ambiguity aversion is transmitted into portfolio choice. In complete markets, ambiguity aversion toward a particular risk operates primarily through the corresponding exposure, with small cross-risk effects. In incomplete markets, ambiguity aversion is jointly transmitted through the stock position, with predominantly own-regime and small cross-regime effects. Business-cycle transition ambiguity aversion exhibits directional asymmetry, with normal-to-crisis ambiguity aversion generating larger policy and welfare effects than the reverse. Market completeness also changes the relative welfare importance of ambiguity aversion. Normal-to-crisis transition ambiguity aversion has the largest effect in complete markets, whereas diffusion-risk ambiguity aversion generally dominates in incomplete markets. Overall, the economic consequences of business-cycle ambiguity depend critically on transition direction and market completeness.<\/jats:p>","DOI":"10.2139\/ssrn.7597409","type":"posted-content","created":{"date-parts":[[2026,10,11]],"date-time":"2026-10-11T15:45:19Z","timestamp":1791733519000},"source":"Crossref","is-referenced-by-count":0,"title":["Robust Portfolio Choice under Business-Cycle 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