Question

1. why does the effective annual rate often differ from that which the company advertises?

because the effective interest rate takes into account that the calculations are done more than once per year.
because the actual interest rate doesnt take into account the cost of administrative services.
because of depreciation of the rate over time.
because the actual interest rate doesnt take into account the cost of state taxes; it only incorporates the minimum federal tax.

Explanation:

Companies typically advertise the nominal annual interest rate, which does not account for compounding. The effective annual rate (EAR) adjusts for compounding that occurs multiple times within a year (e.g., monthly, quarterly), reflecting the true annual cost or return. The other options are incorrect: administrative costs, depreciation of rates, and tax structure differences are not the core reason for the gap between advertised and effective annual rates.

Answer:

Because the effective interest rate takes into account that the calculations are done more than once per year.