Non-Additivity of Subjective Expectations over Different Time Intervals

Haan, Peter; Sun, Chen; Sunde, Uwe; Weizsäcker, Georg (9. September 2022): Non-Additivity of Subjective Expectations over Different Time Intervals. Collaborative Research Center Transregio 190, Discussion Paper No. 337

Abstract

We examine the additivity of stock-market expectations over different time intervals. When asked about a ten-year interval, survey respondents expect a stock-price change that is not equal to, but closer to zero than, the sum of their expectations over two shorter time intervals that cover the same ten years. Such sub-additivity is irrational in that it cannot stem from aggregating short-term expectations. Model estimates show that the pattern is consistent with a time perception where shorter time intervals have a proportionally larger weight. We also find that the respondents' degree of additivity is correlated with making larger financial investments.

• Item Type: Paper (Discussion Paper)
• Keywords: expectation formation; time perception; sub-additivity; super-additivity
• Faculties: Economics > Collaborative Research Center Transregio "Rationality and Competition"
• Subjects: 300 Social sciences > 330 Economics
• JEL Classification: D01, D14, D84, D9
• Language: English