# Permutation Entropy and Information Recovery in Nonlinear Dynamic Economic Time Series

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## Abstract

**:**

## 1. Introduction

The 1000-point collapse of the Dow Jones Industrial Average on 6 May 2010 “… was a small indicator of how complex and chaotic, in the formal sense, these systems have become …” Ben Bernanke, Interview with the International Herald Tribune, 17 May 2010

#### Looking Ahead

## 2. Permutation Entropy and Ordinal Patterns

**p**and

**q**so that it is referred as a power divergence measure.

_{s−3}, x

_{s−2}, x

_{s−1}, x

_{s}). Following Equation (3), we found that ${x}_{s-3}\le {x}_{s-2}\le {x}_{s}\le {x}_{s-1}$. After this, the ordinal pattern that allows us to fulfill Equation (2) is $\left[3,2,0,1\right]$. The second 4-dimensional vector is $\left(3,5,4,2\right)$ and $\left[0,3,1,2\right]$ will be its associated permutation and so on. A graphical example for $D=3$ is presented in Appendix A.

## 3. Information Theoretic Estimation and Inference Base

#### The Cressie–Read Family of Power Divergence Measures and the PE metric

## 4. Estimation and Empirical Applications

#### 4.1. PE Information Recovery Estimation

#### 4.2. Analysis of the Full DJIA Time Series: 1901–2016

#### 4.3 Rolling Window Analysis

#### 4.4. Post-World War II Analysis

#### 4.5. Rolling Window Analysis

## 5. Concluding Remarks

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Appendix A

## Appendix B

Time Period | ||||
---|---|---|---|---|

Permutation | 1901–2016 | 2000–2016 | ||

Count | Relative Freq. | Count | Relative Freq. | |

$\mathrm{p}\left({\pi}_{i}\right)$ | $\mathrm{p}\left({\pi}_{i}\right)$ | |||

${\pi}_{1234}$ | 1259 | 0.04 | 118 | 0.028 |

${\pi}_{1243}$ | 1369 | 0.043 | 154 | 0.036 |

${\pi}_{1324}$ | 1108 | 0.035 | 164 | 0.038 |

${\pi}_{1342}$ | 1388 | 0.044 | 187 | 0.044 |

${\pi}_{1423}$ | 1167 | 0.037 | 202 | 0.047 |

${\pi}_{1432}$ | 1407 | 0.045 | 197 | 0.046 |

${\pi}_{2134}$ | 1456 | 0.046 | 154 | 0.036 |

${\pi}_{2143}$ | 1357 | 0.043 | 188 | 0.044 |

${\pi}_{2314}$ | 1136 | 0.036 | 172 | 0.04 |

${\pi}_{2341}$ | 1176 | 0.037 | 143 | 0.033 |

${\pi}_{2413}$ | 1095 | 0.035 | 179 | 0.042 |

${\pi}_{2431}$ | 1460 | 0.046 | 184 | 0.043 |

${\pi}_{3124}$ | 1332 | 0.043 | 171 | 0.04 |

${\pi}_{3142}$ | 1265 | 0.04 | 225 | 0.053 |

${\pi}_{3214}$ | 1459 | 0.046 | 223 | 0.052 |

${\pi}_{3241}$ | 1077 | 0.034 | 195 | 0.046 |

${\pi}_{3412}$ | 1177 | 0.037 | 162 | 0.038 |

${\pi}_{3421}$ | 1538 | 0.049 | 186 | 0.043 |

${\pi}_{4123}$ | 1145 | 0.036 | 158 | 0.037 |

${\pi}_{4132}$ | 1151 | 0.037 | 181 | 0.042 |

${\pi}_{4213}$ | 1452 | 0.046 | 203 | 0.047 |

${\pi}_{4231}$ | 1305 | 0.041 | 174 | 0.041 |

${\pi}_{4312}$ | 1494 | 0.047 | 141 | 0.033 |

${\pi}_{4321}$ | 1719 | 0.055 | 218 | 0.051 |

Total | 31,492 | 1 | 4279 | 1 |

## Appendix C

**Table A2.**Single Normalized Permutation Entropy, $P{E}_{D,norm}$, Point Estimates of DJIA Returns for Different Embedding Dimensions and Different Window Lengths.

PE | ||||
---|---|---|---|---|

Period | T | D = 4 | D = 5 | D = 6 |

1901–2016 | 31,495 | 0.998 | 0.997 | 0.995 |

2000–2016 | 4282 | 0.997 | 0.994 | 0.983 |

2007–2009 | 755 | 0.992 | 0.975 | 0.91 |

**Note**: T denotes the length of the time series (the window length), while D is the embedding dimension.

## Appendix D. Computational Implications

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**Figure 1.**(

**a**) Daily Closing DJIA nominal price index for the period of 5 January 1901–30 December 2016 and shaded recession regions from the National Bureau of Economic Research (NBER) record of economic cycles (see http://www.nber.org/cycles.html); (

**b**) Daily DJIA nominal continuously compounded returns over the period of 7 January 1901–30 December 2016 with kurtosis for ${r}_{t}$ of 24.66, which shows the characteristic fat-tailed behavior compared with a normal distribution.

**Figure 2.**Series of normalized permutation entropy, $P{E}_{D,norm}$, rolling estimates for 750-day $\left(\simeq 3\text{}\mathrm{years}\right)$ segments, a fixed time delay $\tau =1$ and embedding dimension $D=5$ of daily DJIA nominal returns. In this plot, equal return values have been numerically broken by adding white noise to the time series, with the Gaussian noise being smaller than the smallest distance between values. The dates in this plot are start-dates of each segment.

**Figure 3.**(

**a**) Daily Closing DJIA nominal price index for the period 3 January 2000–30 December 2016 (T = 4283 observations) and shaded recession region from the NBER record of economic cycles (see http://www.nber.org/cycles.html). The left and right dash red vertical lines denote the dates on which the DJIA hit an intra-day peak of 14,164.53 (9 October 2007) and its lowest value 6547.05 (9 March 2009), respectively; (

**b**) Daily DJIA nominal continuously compounded returns.

**Figure 4.**Series of normalized permutation entropy, $P{E}_{D,norm}$, rolling estimates for 750-day $\left(\simeq 3\text{}\mathrm{years}\right)$ segments, a fixed time delay $\tau =1$ and embedding dimension $D=5$ of daily DJIA nominal returns. In the plot, equal values have been numerically broken by adding white noise to the time series, with the Gaussian noise being smaller than the smallest distance between values. The shaded region denotes the NBER Recession (December 2007–June 2009). The dates in this plot are start-dates of each segment.

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Henry, M.; Judge, G.
Permutation Entropy and Information Recovery in Nonlinear Dynamic Economic Time Series. *Econometrics* **2019**, *7*, 10.
https://doi.org/10.3390/econometrics7010010

**AMA Style**

Henry M, Judge G.
Permutation Entropy and Information Recovery in Nonlinear Dynamic Economic Time Series. *Econometrics*. 2019; 7(1):10.
https://doi.org/10.3390/econometrics7010010

**Chicago/Turabian Style**

Henry, Miguel, and George Judge.
2019. "Permutation Entropy and Information Recovery in Nonlinear Dynamic Economic Time Series" *Econometrics* 7, no. 1: 10.
https://doi.org/10.3390/econometrics7010010