This is a prepublication version of J.M. Beddow, T.M. Hurley, P.G. Pardey, and J.M. Alston’s “Food Security: Yield Gap” chapter in N. Van Alfen, editor-in-chief, Encyclopedia of Agriculture and Food Systems, Vol. 3, San Diego: Elsevier, 2014, pp. 352-365.

Some studies have reported a slowdown in U.S. farm productivity growth, but the prevalent view among economists is to reject or downplay the slowdown hypothesis, implying that the rates of productivity growth experienced over the past half century can be projected forward. We set out to resolve...

This paper begins with a review of the methods and assumptions used to measure capital service flows. Two data series on capital inputs in U.S. agriculture are briefly described and compared. We show that measures of capital services are sensitive to the treatment of interest rates. Notably, the...

Reported rates of return to agricultural R&D are generally high, but they are likely to be biased, particularly because of attribution problems—mismatching research benefits with costs. The importance of attribution biases is illustrated here with new evidence for Brazil. During 1981–2003,...

Annual data for forty-eight states are used to account for changes in the composition of input and output aggregates over space and time, and thereby to obtain new evidence on changes in inputs, outputs, and productivity in U.S. agriculture. The measures change significantly when we use...

Governments everywhere are trimming their support for agricultural R&D, giving greater scrutiny to the support that they do provide, and reforming the public agencies that fund, oversee, and carry out the research. This represents a break from previous patterns, which had consisted of expansion...

A total of 289 studies of returns to agricultural R&D were compiled and these provide 1821 estimates of rates of return. After removing statistical outliers and incomplete observations, across the remaining 1128 observations the estimated annual rates of return averaged 65 per cent overall —...

We use newly constructed state-specific data to explore the implications of common modeling choices for measures of research returns. Our results indicate that state-to-state spillover effects are important, that the research and development lag is longer than many studies have allowed, and that...