Appendix 1—table 1. ${\displaystyle r^2}$ values obtained for each experimental dataset ${\displaystyle \{A;B\}}$ when performing a linear regression analysis on ${\displaystyle \{A;B\}}$ directly (‘Linear’) and on the ${\displaystyle ln(A)-ln(B)}$ (‘Power’) and ${\displaystyle ln(A)-B}$ (‘Exponential’) transformations of ${\displaystyle \{A;B\}}$.

The $r^2$ values returned by the three types of regression cannot be directly compared to estimate the best model. However, the power fit returned ${\displaystyle r^2>0.5}$ for relatively more experimental datasets than the linear and exponential fits.

	Studies	Linear	Power	Exponential
${\displaystyle \left\{ACV;S_{MN}\right\}}$	Cullheim, 1978	0.42	0.45	0.43
	Kernell and Zwaagstra, 1981	0.62	0.63	0.6
	Burke et al., 1982	0.23	0.26	0.24
${\displaystyle \left\{AHP;S_{MN}\right\}}$	Zwaagstra and Kernell, 1980	0.33	0.37	0.35
${\displaystyle \left\{AHP;ACV\right\}}$	Eccles et al., 1958b	0.53	0.54	0.54
	Zwaagstra and Kernell, 1980	0.42	0.44	0.42
	Gustafsson and Pinter, 1984a	0.71	0.68	0.7
	Foehring et al., 1987	0.15	0.14	0.14
${\displaystyle \left\{R;S_{MN}\right\}}$	Kernell and Zwaagstra, 1981	0.68	0.71	0.7
	Burke et al., 1982	0.41	0.5	0.46
${\displaystyle \left\{R;ACV\right\}}$	Kernell, 1966	0.70	0.65	0.64
	Burke, 1968	0.28	0.31	0.31
	Kernell and Zwaagstra, 1981	0.68	0.71	0.71
	Fleshman et al., 1981	0.3	0.21	0.2
	Gustafsson and Pinter, 1984a	0.45	0.44	0.42
	Sasaki, 1991	0.68	0.68	0.66
${\displaystyle \left\{R;AHP\right\}}$	Gustafsson, 1979	0.43	0.41	0.42
	Gustafsson and Pinter, 1984a	0.71	0.68	0.67
	Foehring et al., 1987	0.33	0.32	0.33
	Pinter and Vanden Noven, 1989	0.66	0.53	0.59
	Sasaki, 1991	0.57	0.49	0.52
${\displaystyle \left\{I_{th};R\right\}}$	Kernell, 1966	0.52	0.52	0.68
	Fleshman et al., 1981	0.28	0.34	0.38
	Gustafsson and Pinter, 1984b	0.63	0.83	0.83
	Zengel et al., 1985	0.49	0.6	0.62
	Munson et al., 1986	0.34	0.42	0.47
	Foehring et al., 1987	0.34	0.47	0.47
	Krawitz et al., 2001	0.32	0.49	0.44
${\displaystyle \left\{I_{th};ACV\right\}}$	Kernell and Zwaagstra, 1981	0.23	0.24	0.24
	Gustafsson and Pinter, 1984b	0.4	0.52	0.5
${\displaystyle \left\{I_{th};AHP\right\}}$	Gustafsson and Pinter, 1984b	0.55	0.72	0.69
${\displaystyle \left\{C;R\right\}}$	Gustafsson and Pinter, 1984a	0.55	0.57	0.57
${\displaystyle \left\{C;I_{th}\right\}}$	Gustafsson and Pinter, 1984a	0.23	0.34	0.24
${\displaystyle \left\{C;AHP\right\}}$	Gustafsson and Pinter, 1984a	0.25	0.26	0.26
${\displaystyle \left\{C;ACV\right\}}$	Gustafsson and Pinter, 1984a	0.17	0.22	0.19
${\displaystyle \left\{\tau ;R\right\}}$	Burke and ten Bruggencate, 1971	0.04	0.07	0.03
	Gustafsson, 1979	0.6	0.63	0.61
	Gustafsson and Pinter, 1984a	0.63	0.69	0.59
	Zengel et al., 1985	0.39	0.33	0.36
	Pinter and Vanden Noven, 1989	0.65	0.69	0.62
	Sasaki, 1991	0.68	0.72	0.64
${\displaystyle \left\{\tau ;I_{th}\right\}}$	Gustafsson and Pinter, 1984b	0.63	0.59	0.57
${\displaystyle \left\{\tau ;ACV\right\}}$	Gustafsson and Pinter, 1984a	0.69	0.76	0.76
${\displaystyle \left\{\tau ;AHP\right\}}$	Gustafsson and Pinter, 1984a	0.34	0.32	0.31