ST Oct 17, 2007
80% of readers say ST is important to their lives
By Oo Gin Lee
……. Addressing the Forum writers in the auditorium at Singapore Press Holdings' Toa Payoh premises, ST editor Han Fook Kwang noted that a readership survey in April found that nearly eight in 10 of the paper's readers polled in face-to-face interviews considered it an 'important' or 'must-read'.
Aha. Here we see something known as “survivorship bias” at work. The flaw in the survey is that its sample population comprises only people who currently still read the Straits Times. Thus the survey excludes all those people who had already stopped reading the Straits Times precisely because they considered the Straits Times to be “unimportant” or “unnecessary”.
Survivorship bias is a concept often mentioned in the financial world, in relation to the performance of unit trusts and mutual funds. For example, a fund manager may claim that more than 75% of its funds have outperformed the industry average. This sounds like an impressive statistic - until you find out how many funds the manager had already shut down, precisely because they performed below the industry average.
We say that there is a "survivorship bias", because the "more than 75%" statistic is based only on the funds that still survive. Those funds which had already died from their own poor performance are conveniently dropped from the survey.