Existing empirical evidence on the impact of macroeconomic variables on agriculture remains mixed and inconclusive. This paper re-examines the dynamic relationship between monetary policy variables and agricultural prices using alternative vector autoregression (VAR) type model specifications. Directed acyclic graph theory is proposed as an alternative modeling approach to supplement existing modeling methods. Similar to results in other studies, this study's findings show that over the time period analyzed (1975–2000), changes to money supply as a monetary policy tool had little or no impact on agricultural prices. The primary macroeconomic policy instrument that affects agricultural prices is the exchange rate, which is shown to be directly linked to interest rate, a source of monetary policy shock.

Using advanced methods of directed acyclic graphs with Bernanke structural vector autoregression models, this article extends recent econometric research on quarterly U.S. markets for wheat and wheat-based value-added products downstream. Analyses of impulse response simulations and forecast error variance decompositions provide updated estimates of market elasticity parameters that drive these markets, and updated policy-relevant information on how these quarterly markets run and dynamically interact. Results suggest that movements in wheat and downstream wheat-based markets strongly influence each other, although most of these effects occur at the longer-run horizons beyond a single crop cycle.

This study used aggregated data for fresh vegetables and fresh fruits toanalyze how trade flows in the fresh produce industry have changed undertrade agreements and to assess the potential implications to nutritionpolicies in the United States. The first part of the analysis uses aBai-Perron test to endogenously determine any structural break points invegetable and fruit trade movements and prices. Directed acyclic graphs andhistorical decompositions are used to establish causal patterns oninnovations from vector autoregression models fitted to annual observationsof trade flows, prices, and income. The results showed that trade agreementshave had significant impacts to the produce industry. Income was a majordeterminant of domestic fruit production and imports.

This study investigates the potential impacts of food safety outbreaks on domestic shipments, imports, and prices of the produce industry. Three case studies were analyzed to assess these potential impacts: the cantaloupe outbreak of March–April 2008, the spinach outbreak of September 2006, and the tomato outbreak of June–July 2008. Data-determined historical decompositions were conducted to provide a weekly picture of domestic shipment, import, and price fluctuation transmissions. The empirical analysis based on a vector autoregression (VAR) model showed differences in the results depending on the source of the outbreak (domestic vs. imported).

We present a categorical formulation of the rewriting of possibly cyclic term graphs, based on a variation of algebraic 2-theories. We show that this presentation is equivalent to the well-accepted operational definition proposed by Barendregt et al. – but for the case of circular redexes , for which we propose (and justify formally) a different treatment. The categorical framework allows us to model in a concise way also automatic garbage collection and rules for sharing/unsharing and folding/unfolding of structures, and to relate term graph rewriting to other rewriting formalisms.