This paper analyzes four years of worldwide sales data for wave and ski boards to evaluate the effectiveness of several demand-forecasting techniques. Using Microsoft Excel's Data Analysis Pack, the author compares simple averaging, moving average, median values, and exponential smoothing to determine which method best captures seasonal fluctuations and underlying growth trends. The analysis finds that exponential smoothing most effectively filters out random "noise" in the data, making it the preferred method for projecting Year 5 inventory. The paper also notes a compound annual growth rate of 4.76% across the period and identifies the key seasonal drivers behind sales spikes in spring and fall.
The following analysis is based on sales data for sporting goods, graphed over the last four years, showing worldwide demand for wave and ski boards combined. Each data point on the graphic represents combined sales of wave and ski boards. The significant ramp in sales throughout March and April is attributable to the launch of each season's new wave boards. The spike in sales in October is attributable to ski board sales increasing on a seasonal basis. In aggregate, the market continues to grow for these products, generating a compound annual growth rate (CAGR) of 4.76% across the four-year period. Using averaging based on four periods generates the averaging line shown in the graphic.
A relatively simplistic approach to defining Year 5's inventory does not necessarily capture the variation in forecasts observed over the four previous years. As can be seen from the graphic, simple averaging only amplifies the variation in the data series; it does not explain which factors are causing the variation overall (Ziegel, 2006). A more robust forecasting technique is therefore needed — one that takes into account periodic fluctuations in value rather than smoothing them away indiscriminately.
The following analysis was completed using the Moving Average feature of the Data Analysis Pack installed in Microsoft Excel 2010. The orange line shows the relative goodness of fit for the data overall, identifying May as the month with the highest demand and therefore the most difficult month to forecast accurately. December's low inventory levels illustrate how wave and ski boards are popular gifts during the holiday season, creating a distinctive dip in the demand curve.
"Median, smoothing, and moving average compared"
The use of the exponential method of analysis delivers the most accurate forecast in that the errant or "noise" factors inherent in the sales data are mitigated through the approach to defining exponential forecast values. Forecasting techniques that account for exponential weighting over simple time series better reflect recurrent trends rather than random fluctuations (Ziegel, 2006). This analysis demonstrates how these elements of forecasting interchange with one another and supports exponential smoothing as the preferred method for projecting Year 5 inventory requirements.
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