Why when assuming constant dividend pay-out assumption, the capital structure will vary from year to year? Can someone help me please. I don't understand.

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If Nancy Smith doesn't want to allow dividend payout to vary across the years, then she can hold the dividend payout constant. However, then she will have to allow for the capital structure to vary from year to year, since a constant dividend payout may not result in a stream of equity values that will result in a constant debt to equity ratio. If the capital structure is allowed to vary, then the cost of capital will vary each period as well.