INSERT FIGURE 1
To forecast ZT/CA data we, first, used the simplest of the exponentially smoothing (SES) method. This method is suitable for forecasting data with no clear trend or seasonal pattern, such as ZT/CA data. Yet, ZT/CA data show a rise in the last few years, suggesting a trend in data. Therefore, we used the Gardner & McKenzie (1985) approach that uses a parameter that “dampens” the trend to a flat line sometime in the future. Methods that include a damped trend have proven to be very successful and are arguably the most popular individual methods when exponential forecasts are required.