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So the survivorship bias and the backfill bias would be much,much more of a problem in the hedge fund world.
所以生存偏差和回填偏差,会是对冲基金领域里一个相当重大的问题
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Looking at this particular group, he estimated survivorship bias to be 4.4% per year and backfill bias to be 7.3% per year.
分析这个特定的样本,他估算其生存偏差每年达到4.4%,回填偏差每年达到7.3%
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Then if you adjust for survivorship bias, you end up concluding that the deficit wasn't .3% but the deficit was actually 2%.
那么如果你算上生存偏差,你会发现,缺口不是0.3%,事实上是2%
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So,the combination of survivorship bias and backfill bias for that one year made 4.3 percentage points difference.
因此在生存偏差和回填偏差的共同作用下,造成了两个收益率之间4.3%的差值
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You've got survivorship bias taking out bad records and then you've got backfill bias adding good records.
生存偏差去掉了那些糟糕的记录,回填误差又加入了一些好的记录
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Now,more than 130 managers failed because, in addition to survivorship bias, there's something called backfill bias.
其实失败的经理人超过130位,因为除了生存偏差之外,还有称为回填偏差的影响
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So,we're talking about a group of funds that in aggregate probably produced somewhere in the low teens returns and he's got 11.7% per year combined survivorship bias and backfill bias.
因此我们说这组基金总体上,大概产生了略高于10%的收益率,他算出的数字是每年11.7%,结合了生存偏差和回填偏差
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Roger Ibbotson took a look at a larger group of funds -3,500--funds over a ten-year period and found survivorship bias at 2.9% per year and backfill bias at 4.6% per year.
罗杰·伊博森研究了更大的样本组,3500支基金10年间的表现,算出其生存偏差是每年2.9%,回填偏差是每年4.6%
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How important is this survivorship bias?
生存偏差有多重要
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This is true whether you look at the universe of the mutual fund managers that we might have available to us as individuals or whether it's institutional data, such as those that I just cited; that concept is survivorship bias.
的确如此,不论你在观察,可接触到的基金经理个人,还是观察一些机构数据,就像我刚引用过的那些,这个现象就是生存偏差
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In the case of Burt Malkiel's data, more than 11% per year and in the case of Roger Ibbotson's data between 7% and 8% per year of those returns can be explained either by backfill bias or survivorship bias.
在伯特·麦基尔的数据中,超过11%的年平均收益,在罗杰·伊博森的数据中,7%到8%的年平均收益,可以用生存偏差或回填偏差来解释
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