... (equation 18), the results reject the null hypothesis in each case at a 0.05 critical value, indicating that the underlying production technology in the paper and paperboard industry is neither homogeneous ... energy (labor) use resulting in an increase in the labor-energy (energy-labor) input ratio, that is, raising the input price increases the relative use of the other input consistent with a substitution ... price inelastic in the early part of the sample, during the oil price shocks of the 1970s, there was a dramatic and permanent increase, in absolute value, in the own price elasticity of demand,...