PPI of copper ores and grains: update. July and August 2009

Lately, we have demonstrated that the evolution of various components of CPI and PPI in the United States is not a random process but rather a predetermined one with long-term sustainable trends [1-4]. Using these trends, one can predict consumer and producer price indices for various goods, services and commodities [5-7]. Moreover, share prices for selected S&P 500 companies are also well described in the past by the differences in the PPI and CPI [8,9]. The near future will test the predictive power of our model.
In [4-7], we presented the evolution many commodities with varying weight in the PPI. But there are many more commodities of interest for producers, consumers and investors. In this article, we present the producer price indices of copper and grain. The evolution of the indices of these two commodities is independent, but both give a good example of the absence of clear sustainable trends. In other words, not every commodity price is predictable as an extension of a liner trend, as mentioned in [4]. However, in the short-term, there is observed some inertia in the evolution of both prices. Therefore, one can predict the indices at a several month horizon. On July 27, we published selected results of our study for June 2009. This is a bi-monthly update, which includes two new readings for July and August 2009. Both commodities demonstrate continuation of short-term trends. Supposedly, these trends survive till the end of 2009.
Figure 1 displays the overall (commodity) PPI and the index of copper ores since 1988. The difference of these two indices has a remarkable history; no big change between 1988 and 2005, and then a sudden giant jump in the copper index. Fluctuations between 350 and 500 points lasted three years, and then the index dropped by ~300 units back to the PPI level. Despite the early start in 2005 the growth seems to be oil independent, the most recent fall looks to be driven by oil price and the overall economic slowdown. In July and August 2009, one can observe a sustainable increase in the cooper index likely associated with the rise in oil price. In the long-run, oil price should decline to the level of ~$25 in 2016. Therefore, copper price will likely not be growing to its peak in April 2008 (491.7), but will likely return to heights around 350. (Our model based on the presence of sustainable trends in the difference between the PPI and individual PPI is not applicable to copper ores.)

Figure 1. Evolution of the price index of copper ores and the PPI.

The producer price index for grains presents another difficult case. Figure 2 depicts the PPI and the index, and their difference between 1960 and 2009. There is no sustainable trend in the difference. Between 1974 and 2005, the difference demonstrated an overall growth with several spikes, the strongest one in 1996. The presence of a long-term positive trend in the difference is completely due to the growth in the PPI because the index of grains fluctuates around a constant level just slightly above 100 points. Lately, the grains index suffered the biggest rise and fall in absolute terms. The main increase started earlier in 2007 and stretched into 2008, with the peak in June 2008. Volatility of the difference during the past two years was so high that it is difficult to predict the next move of the price index of grains at a several year horizon. Seemingly, it has been repeating the trajectory of the index for crude oil in 2008 and 2009. If it is the case, one can expect that the index for grains will continue to oscillate around the constant level of ~100.

It is instructive to compare two major spikes in the grains index in 1996 and 2008 relative to the PPI. In order to avoid comparing absolute values, which undergo secular growth, the evolution of the difference between the PPI and the price index of grains normalized to the PPI. Figure 3 presents the normalized curves. The left panel shows that the spike in the grains PPI in July 1996 is similar in relative terms to that observed in 2008. The right panel tests this hypothesis: the spikes are synchronized - for the black line is shifted forward by 142 months. From this comparison, it is likely that decline in the grains index relative to the PPI will extend into the 2010s.

Figure 2. Evolution of the price index of grains and the PPI.

Figure 3. Evolution of the difference between the PPI and the price index of grains normalized to the PPI. Left panel shows that the spike in the grains PPI in July 1996 is similar to that observed in 2009. Right panel tests this hypothesis – the spikes are synchronized (time shift by 142 months). One might expect a decline in the grains index relative to the PPI will be extended into the 2010s.

In the short-run, the index for copper will be growing at least till the end of 2009. The index for grains will continue its decline relative to the PPI. As a consequence, one can expect that the index for food will be also decreasing and this decline will stretch into the 2010s.
In the long run, the producer price index for copper and that of grains both demonstrate practically unpredictable behavior with unclear future. This observation only emphasizes the importance of sustainable trends observed for other commodities. In the US economy, as in many natural systems, there exist trend components, oscillating components, and random components.

1. Kitov, I., Kitov, O., (2008). Long-Term Linear Trends In Consumer Price Indices, Journal of Applied Economic Sciences, Spiru Haret University, Faculty of Financial Management and Accounting Craiova, vol. 3(2(4)_Summ), pp. 101-112.
2. Kitov, I., (2009). Apples and oranges: relative growth rate of consumer price indices, MPRA Paper 13587, University Library of Munich, Germany.
3. Kitov, I., Kitov, O., (2009). A fair price for motor fuel in the United States, MPRA Paper 15039, University Library of Munich, Germany,
4. Kitov, I., Kitov, O., (2009). Sustainable trends in producer price indices, Journal of Applied Research in Finance, v. 1, (in press)
5. Kitov, I., Kitov, O., (2009). PPI of durable and nondurable goods: 1985-2016, MPRA Paper 15874, University Library of Munich, Germany
6. Kitov, I., (2009). Predicting gold ores price, MPRA Paper 15873, University Library of Munich, Germany
7. Kitov, I., (2009). Predicting the price index for jewelry and jewelry products: 2009-2016, MPRA Paper 15875, University Library of Munich, Germany
8. Kitov, I., Kitov, O., (2009). Predicting share price of energy companies: June-September 2009, MPRA Paper 15863, University Library of Munich, Germany
9. Kitov, I., Kitov, O., (2009). Modelling selected S&P 500 share prices, MPRA Paper 15862, University Library of Munich, Germany

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