Variables used in models
| Variable | Description | Source |
|---|---|---|
| wheat_pln | Purchase price of wheat (PLN/t) | CSO in Poland |
| corn_pln | Purchase price of corn (PLN/t) | CSO in Poland |
| rapeseed_pln | Purchase price of rapeseed (PLN/t) | Ministry of Agriculture |
| wheat_crop | Wheat harvest volume in Poland (annual data) | Eurostat |
| corn_crop | Corn harvest volume in Poland (annual data) | Eurostat |
| rapeseed_crop | Rapeseed harvest volume in Poland (annual data) | Eurostat |
| wheat_eur_f | Wheat futures price at the end of the month (EUR/t) | Euronext |
| corn_eur_f | Corn futures price at the end of the month (EUR/t) | Euronext |
| rapeseed_eur_f | Rapeseed futures price at the end of the month (EUR/t) | Euronext |
| eurpln | EUR/PLN exchange rate at the end of the month | NBP |
| eurpln_sd | Standard deviation of the EUR/PLN exchange rate in each month calculated from daily quotations | Own calculations, NBP |
| freight | Sea freight price index on the European grain market at the end of the month (2013 = 100) | Own calculations, IGC* |
Error correction models
| Wheat | Corn | Rapeseed | |
|---|---|---|---|
| eurpln | 0.665*** | 0.948* | 0.898*** |
| wheat_eur_f | 1.05*** | ||
| corn_eur_f | 0.922*** | ||
| rapeseed_eur_f | 0.946*** | ||
| cons | 0.157 | 0.347 | 0.487* |
| EC term (t – 1) | –0.245** | –0.530*** | –0.511*** |
| Δ eurpln (t – 1) | 0.488 | –1.510** | –0.265 |
| Δ wheat_pl (t – 1) | 0.217* | ||
| Δ wheat_eur_f (t – 1) | 0.211* | ||
| Δ corn_pl (t – 1) | 0.417*** | ||
| Δ corn_eur_f (t – 1) | 0.085 | ||
| Δ rapeseed_pl (t – 1) | 0.218** | ||
| Δ rapeseed_eur_f (t – 1) | 0.008 | ||
| Cons | 0.001 | 0.002 | 0.002 |
| R2 | 0.401 104 | 0.380 104 | 0.604 104 |
| N | 104 | 104 | 104 |
Wheat: the reaction function to changes in the price of futures contracts for wheat, corn, and rapeseed (EUR) depending on the level and volatility of the EUR/PLN exchange rate
| Month | ||||||||
|---|---|---|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | ||
| Wheat | Appreciation | 0.630*** | 0.922*** | 1.078** | 1.340* | 1.278 | 1.267 | 1.386 |
| Depreciation | 0.823*** | 1.379*** | 1.467*** | 1.485*** | 1.652*** | 1.601** | 1.816** | |
| Difference | 0.455 | 0.309 | 0.594 | 0.884 | 0.760 | 0.819 | 0.801 | |
| Low Vol. | 0.570*** | 1.134*** | 1.405*** | 1.716*** | 1.886*** | 1.824** | 1.612* | |
| High Vol. | 0.968*** | 1.442*** | 1.512*** | 1.467** | 1.565** | 1.622* | 2.375** | |
| Diff (t-test) | 0.139 | 0.502 | 0.885 | 0.806 | 0.794 | 0.889 | 0.647 | |
| Corn | Appreciation | –0.192 | –0.474 | 0.746 | 1.768* | 1.618 | 0.910 | 1.500 |
| Depreciation | 0.675** | 1.847*** | 1.934*** | 1.877** | 2.571*** | 3.100*** | 3.126*** | |
| Difference | 0.234 | 0.018 | 0.310 | 0.938 | 0.550 | 0.228 | 0.408 | |
| Low Vol | –0.370 | –0.247 | 1.245* | 1.800** | 2.379** | 3.551*** | 3.542*** | |
| High Vol. | 1.008*** | 2.073*** | 1.983*** | 2.244*** | 2.552*** | 1.894* | 2.390** | |
| Diff (t-test) | 0.060* | 0.021** | 0.541 | 0.753 | 0.914 | 0.367 | 0.560 | |
| Rapeseed | Appreciation | 0.498 | 0.720 | 0.804 | 0.526 | 0.342 | 0.067 | –0.122 |
| Depreciation | 0.782*** | 1.789*** | 2.340*** | 2.403*** | 2.449*** | 2.710*** | 3.078*** | |
| Difference | 0.456 | 0.050 | 0.047 | 0.097 | 0.152 | 0.119 | 0.094 | |
| Low Vol. | 0.810*** | 1.621*** | 1.735*** | 1.727*** | 1.563** | 1.471* | 1.103 | |
| High Vol. | 0.701*** | 1.594*** | 2.343*** | 2.422*** | 2.570*** | 2.974*** | 3.794*** | |
| Diff (t-test) | 0.738 | 0.954 | 0.357 | 0.457 | 0.405 | 0.277 | 0.077 | |
The reaction function of wheat prices in Poland (PLN) to changes in the price of futures contracts for wheat (in EUR)
| Month | ||||||||
|---|---|---|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | ||
| Wheat | Δ wheat_pl (t – 1) | 0.262*** | 0.437*** | 0.500*** | 0.415** | 0.324 | 0.431* | 0.426* |
| Δ wheat_eur_f | 0.494*** | 0.869*** | 0.999*** | 1.090*** | 1.142*** | 1.195*** | 1.101*** | |
| Δ wheat_eur_f (t – 1) | 0.253*** | 0.322*** | 0.402*** | 0.545*** | 0.637*** | 0.503*** | 0.583*** | |
| Δ eurpln | –0.020 | 0.375 | 0.569 | 0.845* | 0.748 | 1.035** | 1.000* | |
| Δ eurpln (t – 1) | 0.333* | 0.580** | 0.868** | 0.697 | 0.858* | 0.903* | 0.792 | |
| Corn | Δ corn_pl (t – 1) | –0.018 | –0.215 | –0.181 | –0.156 | –0.163 | –0.318 | –0.293 |
| Δ corn_eur_f | 0.228 | 0.331 | 0.742*** | 0.837*** | 1.014*** | 1.061*** | 0.988*** | |
| Δ corn_eur_f (t – 1) | 0.157 | 0.618*** | 0.695*** | 0.885*** | 0.946*** | 0.886*** | 0.931*** | |
| Δ eurpln | 0.839* | 0.431 | 0.789 | 0.508 | 0.754 | 1.883* | 2.641** | |
| Δ eurpln (t – 1) | –0.169 | 0.358 | 0.286 | 0.232 | 0.950 | 2.165** | 1.011 | |
| Rapeseed | Δ rapeseed_pl (t – 1) | 0.172** | –0.017 | –0.033 | 0.152 | 0.248* | 0.347** | 0.343* |
| Δ rapeseed_eur_f | 0.318*** | 0.706*** | 1.037*** | 1.070*** | 0.864*** | 0.979*** | 1.041*** | |
| Δ rapeseed_eur_f (t – 1) | 0.412*** | 0.826*** | 0.846*** | 0.677*** | 0.704*** | 0.744*** | 0.831*** | |
| Δ eurpln | 0.263 | 0.377 | 0.538* | 0.881** | 1.304*** | 1.484*** | 1.396*** | |
| Δ eurpln (t – 1) | –0.078 | 0.164 | 0.458 | 0.578 | 0.910** | 0.788* | 0.812* | |