2026 Value Models

Yakima County Value Models - 2026

Statistical regression modeling of sales provides a foundation for equitable and uniform assessments. The level of assessment is determined in accordance with the Standards on Ratio Studies published by the International Association of Assessing Officers (IAAO). All five models listed below were tested against the applicable statistical performance standards outlined in these guidelines. Each model meets or exceeds the requirements for uniformity, equity, and reliability, as demonstrated by the calculated metrics.

Definitions and explanations of these metrics are provided in the Standards above and are briefly outlined here.

The supporting data, including all verified sales used in the analysis, as well as the SPSS syntax files, SPSS output files, and detailed statistical results, are provided below for review and verification.

Agricultural Land Model

Ratio Statistics for Previous Assessed Total / Sale Price Prior to Model
N	Mean	Median	Weighted Mean	Coefficient of Dispersion
545	0.714	0.636	0.65	0.383
Ratio Statistics for Model Value / Time Adjusted Sales Price
N	Mean	Median	Weighted Mean	Coefficient of Dispersion
459	1	0.965	0.903	0.218
Model Summary
Model	R	R Square	Adjusted R Square	Std. Error of the Estimate
1	0.961	0.924	0.919	0.37719

Residential Land Model

Ratio Statistics for Previous Assessed Total / Sale Price Prior to Model
N	Mean	Median	Weighted Mean	Coefficient of Dispersion
499	0.819	0.764	0.748	0.378
Ratio Statistics for Model Value / Time Adjusted Sales Price
N	Mean	Median	Weighted Mean	Coefficient of Dispersion
459	1	0.965	0.903	0.218
Model Summary
Model	R	R Square	Adjusted R Square	Std. Error of the Estimate
1	0.917	0.841	0.83	0.36184

Condominium Model

Metric	Value	IAAO / Industry Benchmark	Assessment
R	0.9518		Very Strong Linear Correlation
R²	0.9059	≥ 0.80 (residential)	Excellent
Adjusted R²	0.8964	Not substantially lower	Excellent
Standard Error of the Estimate	$25,716	Depends on context; See COV	Contextually Strong
Mean Ratio	1.009	≈ 1.00	Excellent
Median Ratio	1.000	≈ 1.00	Excellent
Weighted Mean Ratio	1.004	≈ 1.00	Excellent
COD	5.84%	5%–15%	Excellent
PRD	1.005	0.98–1.03	Balanced – No Vertical Inequity
PRB	-3.10%	Within ±0.05	Acceptable – Minimal Bias
COV	8.3410%		Acceptable
Relative Std. Error	7.77%	< 15% of mean	Strong
Sales N	274	>100 minimum	Robust Sample
Time Bias (R)	0.000007	~0.00 = No Bias	Excellent – Time Adjustment Effective

Manufactured Home on Real Model

Metric	Result	IAAO / Industry Benchmark	Assessment
R	0.864		Strong Linear Correlation
R²	0.746	≥ 0.70 ( Non- Residential)	Acceptable
Adjusted R2	0.726	Not substantially lower	Acceptable
Std. Error of the Estimate	$40,078	Depends on context; See COV	Acceptable Precision
Mean Ratio	1.013	0.90 - 1.10	Excellent
Median Ratio	1.000	0.90 - 1.10	Excellent
Weighted Mean Ratio	1.002	0.90 - 1.10	Excellent
COD	9.32%	5–20%	Excellent
PRD	1.011	0.98–1.03	Balanced - No Vertical Inequity
PRB	-0.046	Within ±0.05	Acceptable – Minimal Bias
COV	12.75%		Acceptable
Relative Std. Error	12.37%	<15% of mean	Strong
N (Sales)	342	>100 minimum, >1,000 ideal	Robust Sample
Time Bias (R)	0.002	~0.00 = No Bias	Excellent – Time Adjustment Effective

Residential Model

Metric	Result	IAAO / Industry Benchmark	Assessment
R	0.9517		Strong Linear Correlation
R²	0.9057	≥ 0.80 (residential)	Excellent
Adjusted R2	0.9039	Not substantially lower	Excellent
Std. Error of the Estimate	$50,956	Depends on context; See COV	Strong
Mean Ratio	1.007		Excellent
Median Ratio	0.999		Excellent
Weighted Mean	0.995		Excellent
COD	0.0895	5–15%	Excellent
PRD	1.0123	0.98–1.03	Balanced - No Vertical Inequity
PRB	-3.10%	Within ±5%	Acceptable - No Vertical Inequity
COV	12.03%		Acceptable - No Vertical Inequity
Relative Std. Error	12.53%	<15% of mean	Strong
N (Sales)	4,539	>100 minimum, >1,000 ideal	Very robust
Time Bias (R)	0.00003942	~0.00 = No Bias	Excellent – Time Adjustment Effective