Buying and holding a stock index is considered as passive investing. However, the STI is not entirely passive. Every quarter, the STI would be reviewed to determine whether certain stocks should be dropped from or added to the index. This can be likened to active stock selection. How have the stock selections of STI of the past 3 years performed?

Over the past 3 years, there have been 6 changes to the STI component stocks. 1 of them is a forced change, as CapitaMalls Asia (CMA) was privatised and its place in the STI was taken over by Ascendas REIT. All the other 5 changes are voluntary changes. The performance of the stocks removed from the index since their removal till 30 Dec 2016 is shown below.
StockReplacement DatePrice
Then
Price 30/12/16%
Changes
Replacement
CMA04 Jun 142.35NANAA-Reit
JMH21 Sep 15