Errors of Measurement in Output Deflators
研究生产者价格指数（PPI）和普查单位价值比（UVR）两种长期价格变化估计中的测量误差，发现PPI信噪比2.72远高于UVR的0.53，且PPI对产品质量变化的调整不足一半，导致基于PPI的生产率增长估计低估了43%。
In this paper we investigate the incidence of measurement errors in two independent estimates of long-term price change, within the framework of multiple indicators models of price measurement. We develop estimates of the measurement-error variances associated with both the Producer Price Index (PPI) and the Census Unit Value Relative (UVR) . Our estimates provide support for the generally accepted view that the PPI is a far more reliable indicator of long-term price change: the estimated signal-to-noise ratios for the PPI and UVR are 2.72 and 0.53, respectively. Our estimates should be useful for both constructing an optimal indicator of price change, and for identifying econometric models including error-ridden price- or output-growth terms as regressors. Our analysis suggests that scores assigned to product deflators provide useful information about their reliability. By extending our model to explicitly incorporate product-quality change, we are able to assess the importance of the problem posed by quality change for price and productivity measurement. Less than half of quality change, which we estimate to occur at an average annual rate of 1.3 percent, appears to be adjusted for in the PPI. Consequently, estimates of productivity growth based on the PPI underestimate quality-adjusted productivity growth by an estimated 43 percent.