Are infant mortality rate declines exponential? The general pattern of 20th century infant mortality rate decline

Table 1 Results from Box-Cox models in which (IMR^λ-1)/λ is regressed against time

Country	Years	λ	Chi-squared for null that λ= 0 (Logarithmic model)	Chi-squared for null that λ= 1 (Linear Model)
Whole sample		0.077	(22.050) ***	(2131.57) ***
Australia	1921–1999	0.249	(37.750) ***	(153.650) ***
Austria	1947–1999	0.102	(9.200) ***	(165.330) ***
Belgium	1900–1913 1918–1999	0.379	(67.180) ***	(130.450) ***
Canada	1921–1999	0.151	(50.290) ***	(288.830) ***
Denmark	1900–1999	0.260	(40.530) ***	(169.090) ***
Finland	1900–1999	0.356	(58.640) ***	(130.600) ***
France	1900–1999	0.354	(52.030) ***	(118.600) ***
Italy	1900–1999	0.587	(122.850) ***	(63.540) ***
Japan	1947–1999	-0.321	(62.000) ***	(238.210) ***
Netherlands	1900–1999	-0.092	(10.680) ***	(342.410) ***
New Zealand	1947–1999	0.591	(49.640) ***	(27.030) ***
Norway	1900–1999	0.364	(90.730) ***	(169.360) ***
Portugal	1940–1999	0.523	(74.340) ***	(64.170) ***
Spain	1908–1999	0.450	(71.570) ***	(82.540) ***
Sweden	1900–1999	0.192	(39.310) ***	(234.810) ***
Switzerland	1900–1999	0.133	(41.060) ***	(352.000) ***
UK	1900–1999	0.136	(34.220) ***	(310.440) ***
USA	1933–1999	0.040	(0.990)	(168.680) ***

No mortality data are available for Belgium from 1914–1918. USA has IMR time series that is best fit as logarithmic. ***p < 0.01 for likelihood ratio test for null that λ = 0 and λ = 1.

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