“…However, the CES function in Equation (6) cannot be transformed in the same simple manner to a linear equation without approximation, and so numerous other techniques have been developed, as evidenced by the CES sample studies shown in Figure 5. The most popular technique in the sample-used by over half the sample [1,6,46,[77][78][79]82,83]-is direct non-linear estimation of the aggregate function. Though complex, its popularity appears to be increasing, which may be due to the increased availability of econometric guidance [175], off-the-shelf programmes [30], and advances in computing power.…”