While there are many variables that affect the advertised Grand Prize estimate in the Powerball game, game sales and the annuity factor are two crucial ones. Sales of games can be impacted by a variety of factors, including seasonality and large Mega Millions jackpots. Game sales are often higher for a Saturday drawing than for a Wednesday drawing. Another important issue is the annuity factor or the price to fund an annuity prize. The interest rates on assets bought to finance prize payments make up the annuity element. The stated Grand Prize increases as interest rates rise. You might not be aware of it, but economic realities like interest rates have an effect on even the Powerball prize!