Paul R. Yarnold, Ph.D.

Optimal Data Analysis, LLC

Recent research reported support for the *a priori* hypothesis that annual crude mortality rate (ACMR) was higher after widespread commercial usage of toxic chemicals and biocides began in the environment in North Dakota in 1998. UniODA was used to compare ACMR in 1934-1997 versus 1998-2005 (the most current data available). Different county types identified included those for which ACMR increased significantly (*p*<0.05) at the experimentwise criterion; increased significantly (*p*<0.05) at the generalized criterion; had a statistically marginal increase (*p*<0.10) at the generalized criterion; or did not have a statistically significant increase (*p*>0.10) at the generalized criterion. Prior research is extended by investigating the path of ACMR over time for these four county groupings, and for each county considered separately. The pattern of mean ipsative ACMR scores across time, observed for counties experiencing a statistically significant increase in ACMR after 1998, revealed the means fell into three almost perfectly discriminable levels: (a) *low* mean scores (mean *z*<0) seen early (1965 or earlier); (b) *medium* scores (0<z<0.5) in the middle of the series (1966-1985); and (c) *high* scores (mean *z*>0) late in the series (1986 or later). Series achieved mean *z*>1 in 1998, and mean scores observed since 1998 have been among the highest on record.