ABT/ABBV valuations on initial when-issued trading:
Yesterday, the ABBV.WI and ABT.WI when issued post-spinoff shares closed with ABBV.WI comprising 54% of the share price of the existing Abbott shares and ABT.WI comprising 46%. The closing prices were $35.00 and $30.40, respectively.
Inasmuch as the amount of net debt to be held by the two successor companies is not the same, the ratios above do not exactly reflect the enterprise values of the two successor companies; still, the 54% and 46% ratios are close enough for a first-order approximation.