http://corporate.morningstar.com/US/documents/ResearchPapers/Tracking%20Chinese%20Equity%20ETFs%20May%202014.pdf
縮址:https://goo.gl/hj5YbG
第24頁:
Other indices—typically the Net Total Return indices—assume a withholding tax
is paid on dividends, but in practice in certain jurisdictions, either some
portion of or all of this tax can be reclaimed by the ETF’s manager at its
source jurisdiction, provided that there is a branch office in the country
where the tax is levied. This activity, known as tax optimisation or dividend
tax enhancement, can boost a fund’s return relative to its benchmark, but it
can also increase its tracking error.
Both physical and synthetic replication ETFs can be affected by tax
optimisation. In the case of ETFs employing physical replication, this activity
will be carried out at the fund level, directly impacting fund returns, while
in the case of synthetic ETFs, it will be implemented at the level of the
bank(s) standing behind the swap(s) embedded in the fund, thereby indirectly
impacting fund returns. The bank(s) providing the swap(s) can decide whether or
not to pass on any revenues from dividend tax enhancements within the framework
of the swap agreement between the fund manager and the swap providers.

這個只是敘述說有稅務優勢的一方可以有資產累計優勢但是這個計算方式沒有指數追蹤 且iShare沒有詳細公布這方面收支 不會知道基金公司到底是把靠稅務優勢拿到的放到哪邊舉例來說 假設靠稅務拿到0.5%優勢 但是ret只有0.25% 剩下的到底在哪裡?

反向去算，IWDA換算出來的有效稅率在十幾％左右。但基金公司有沒有吃掉一部分好處很難說。只能說買IWDA不至於真的照30%被課稅。