$ABBV-$SGPG is the biggest tax inversion so far by far. I think most long-term investors don't understand that the transaction is taxable for the shareholders of the "former" US company. Since the spin-off from ABT was not taxable, I assume there are a huge number of investors with practicably no tax basis. The tax receipts will be in the $B, with very many unhappy shareholders. $MYL and $SLXP will also produce a lot of capital gain taxes, but nothing like ABBV.
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