Why Tinkering Too Much with Your Portfolio Won't Pay Off

I found the title of this article, circulated on the Australian School of Business newsletter, intriguing. In the age of day traders, I constantly wonder if monthly I should evaluate my portfolio strategy. This article and the research paper that it explains provided an academic view of the issue.

Andrew B. Abel, Janice C. Eberly, and Stavros Panageas, professors at Wharton, Kellogg, and the Booth School of Business at the University of Chicago wrote a highly technical paper entitled, Optimal Inattention to the Stock market with Information Costs and Transaction Costs http://www.nber.org/papers/w15010.pdf?new_window=1 .

The paper makes the assumption that the investor has two accounts, an investment account with equities and a transaction account, a cash account for living expenses.  The paper, additionally, considered two transaction cycles or "observation dates", one that occurred at regular intervals--"time dependent", for example, a monthly withdrawal to cover living expenses; and another that occurred far less frequently--"state dependent", for example, once a decade. To assess transaction costs, the authors included two types, "the value of the investor's time, plus commissions and other charges that apply to any action taken" (p.1).

The authors identified "the period of 'optimal inattention'. "Logic says that the higher the investor's cost of time and money, the longer this period is" (p. 1) They concluded that "it would probably not pay to adjust a portfolio more often than every month or two" given commission and other fees" (p.1).

http://www.nber.org/papers/w15010.pdf?new_window=1