Publications:

17. A. M. Petersen, O. Penner.
    A method for the unbiased comparison of MLB and NBA career statistics across era (pdf)
    Submitted to the MIT Sloan Sports Analytics Conference 2012 (2012).
    
    An extension of "Methods for detrending success metrics to account for inflationary and deflationary factors" to National Basketball Association (NBA) career statistics. Includes extensive tables listing re-ranked top-50 achievements for points, rebounds and assists, at the season and career level.

16. A. M. Petersen, M. Riccaboni, H. E. Stanley, F. Pammolli.
    Persistence and Uncertainty in the Academic Career (pdf)
    Submitted (2011).
    
    Recent shifts in the business structure of universities and a bottleneck in the supply of tenure track positions are two issues that threaten to change the longstanding patronage system in academia. Understanding how institutional changes within academia may affect the overall potential of science requires a better quantitative understanding of how careers evolve over time. Since knowledge spillovers, cumulative advantage, and collaboration are distinctive features of the academic profession, the employment relationship should be designed to account for these factors. We quantify the impact of these factors in the production n_i(t) of a given scientist i by analyzing the longitudinal career data of 300 scientists and compare our results with 21,156 sports careers comprising a non-academic labor force. The increase in the typical size of scientific collaborations has led to the increasingly difficult task of allocating funding and assigning recognition. We use measures of the scientific collaboration radius, which can change dramatically over the course of a career, to provide insight into the role of collaboration in production efficiency. We introduce a model of proportional growth to provide insight into the complex relation between knowledge spillovers, competition, and uncertainty at the individual scale. Our model shows that high competition levels can make careers vulnerable to ``sudden death'' termination relatively early in the career as a result of negative production fluctuations and not necessarily due to lack of individual persistence.

15. A. M. Petersen, J. Tenenbaum, S. Havlin, H. E. Stanley.
    Statistical Laws Governing Fluctuations in Word Use from Word Birth to Word Death (pdf)
    Submitted, (2011).
    
    In this aggregate analysis of the growth rates of millions of words we demonstrate significant signatures of competition driven systems in the linguistic arena of English, Spanish and Hebrew. How often a given word is used, relative to other words, can convey information about the word's linguistic utility. Using Google word data for 3 languages over the 209-year period 1800-2008, we found by analyzing word use an anomalous recent change in the birth and death rates of words, which indicates a shift towards increased levels of competition between words as a result of new standardization technology. We demonstrate unexpected analogies between the growth dynamics of word use and the growth dynamics of economic institutions. Our results support the intriguing concept that a language's lexicon is a generic arena for competition which evolves according to selection laws that are related to social, technological, and political trends. Specifically, the aggregate properties of language show pronounced differences during periods of world conflict, e.g. World War II.
    
    Media coverage:
    
    - Word Extinction , A nice blog summary by Dev Gualtieri (Aug. 11, 2011)
    

14. A. M. Petersen.
    Applications of Statistical Physics to the Social and Economic Sciences (pdf)
    PhD Thesis, Boston University (2011). Thesis Advisor: H. Eugene Stanley
    

13. B. Podobnik, D. Horvatic, A. M. Petersen, B. Urosevic, H. E. Stanley.
    Bankruptcy risk model and empirical tests (pdf)
    Proceedings of the National Academy of Sciences USA 107, 18325 (2010). DOI: 10.1073/pnas.1011942107
    
    We compare bankrupt companies with non-bankrupt companies using Zipf ranking techniques to analyze the debt-to-assets leverage ratio R. Using the distribution of R for bankrupt versus non-bankrupt companies, we estimate the bankruptcy risk of an existing company conditional on its current R value and find that the probability of bankruptcy P(B) ~ R.

12. A. M. Petersen, H. E. Stanley, S. Succi.
    Statistical regularities in the rank-citation profile of scientists (pdf)
    (Nature) Scientific Reports 1, 181 (2011). DOI: 10.1038/srep00181
    
    We analyze the individual career publication statistics of 200 'stellar' physicists and 100 Assistant professors in order to better understand success, productivity, and the h-index. In order to analyze the entire set of publications of a given scientist at once, we analyze the rank-citation curve c(r) using the Zipf ranking technique. Incredibly, we observe universal feature: although every scientist has a distinct h value, each scientist also has a similar (two-parameter) curve c(r)! Using the properties of this universal curve we show that the total number of citations C scales with an author's h-index as C ~ h^(1+\beta), where \beta is a high-rank power-law scaling exponent for c(r). That the human endeavors of these scientists produces a common representative curve suggests that scientific careers are governed by the statistical laws of competition and cumulative advantage. Such statistical regularities in the input-output patterns of scientists can be used as benchmarks for theoretical models of career progress.

11. A. M. Petersen, F, Wang, S. Havlin, H. E. Stanley.
    Market dynamics immediately before and after financial shocks: quantifying the Omori, productivity and Bath laws (pdf)
    Physical Review E 82, 036114 (2010). DOI: 10.1103/PhysRevE.82.036114
    
    Financial shocks (incoming information) can cause significant cascading (e.g. ``market rallies"), so we use methods from earthquake physics to better understand the expected dynamics before and after shocks of characteristic main-shock magnitude M.

10. A. M. Petersen, O. Penner, H. E. Stanley.
    Methods for detrending success metrics to account for inflationary and deflationary factors (pdf)
    Eur. Phys. J. B 79, 67-78 (2011). DOI: 10.1140/epjb/e2010-10647-1
    Pre-print title: Detrending career statistics in professional Baseball: accounting for the Steroids Era and beyond
    
    We compare both career and seasonal achievements of 130+ years of baseball players, (e.g., addressing the question of who effectively hit more home runs -- Babe Ruth or Barry Bonds?), using statistical methods to account for time-dependent factors that inflate success measures. We provide non-technical top-50 record tables for career HR, H, RBI, W, K and season HR, H, RBI, K, focussing on the accessible measures found in newspaper box-scores and on the back of baseball cards.
    
    Media coverage:
    - Complexity Theory and the National Baseball Hall of Fame, the European Physical Journal News Highlights
    - New Statistical Method Ranks Sports Players From Different Eras, MIT Technology Review
    - Boston University clip, The Daily Free Press
    - A Physics Curveball , arts&sciences Fall 2010 Magazine (Annual BU Research Highlight)
    - Baseball Greats Reranked , BU Today, April 8, 2011

9. A. M. Petersen, B. Podobnik, D. Horvatic, H. E. Stanley.
   Scale-invariant properties of public-debt growth (pdf)
   Europhysics Letters 90, 38006 (2010). DOI: 10.1209/0295-5075/90/38006
   
   Applying methods from macro-economic growth theory, we find 'convergence' in country debt-to-GDP leverage ratios over the last 30+ years.

8. A. M. Petersen, F. Wang, H. E. Stanley.
   Methods for measuring the citations and productivity of scientists across time and discipline (pdf)
   Physical Review E 81, 036114 (2010). DOI: 10.1103/PhysRevE.81.036114
   
   If we account for the time-dependent increase in paper citations as well as variations in paper collaboration group size, what do the distributions of (i) career total citations and (ii) career total number of publications look like for individual scientists in highly competitive journals? Also, evidence of cumulative advantage demonstrated by the increasing publication rate of individual scientists with each new publication in his/her career.

7. A. M. Petersen, W-S. Jung, J-S. Yang, H. E. Stanley.
   Quantitative and Empirical demonstration of the Matthew Effect in a study of Career Longevity (pdf)
   Proceedings of the National Academy of Sciences USA 108, 18-23 (2011). DOI: 10.1073/pnas.1016733108
   
   In many competitive systems, there are typically only few "big winners." This largely reflects the everyday fact that obtaining future opportunities often depends on an individual's record of achievement since employment opportunities are limited to a finite number of competitors. We solve exactly a longevity model which predicts the distribution of career length P(x) for professions characterized by high selectivity and uncertainty. We confirm the model's prediction for P(x) using extensive empirical data for the careers of both scientists (publishing in high-impact journals such as Nature, Science, etc.) and professional athletes (playing in MLB, NBA, Premier League, and Korean Professional Baseball). This study uncovers a remarkably simple statistical law which describes the frequencies of the extremely short careers of `one-hit wonders' as well as the extremely long careers of the `iron-horses'. Our model highlights the importance of early career development, showing that many careers are stunted by the relative disadvan- tage associated with inexperience.

6. B. Podobnik, D. Horvatic, A. M. Petersen, H. E. Stanley.
   Cross-Correlations between Volume Change and Price Change (pdf)
   Proceedings of the National Academy of Sciences USA 106, 22079 (2009). DOI: 10.1073/pnas.0911983106
   
   In analogy to the analysis of price volatility in financial markets, we analyze the absolute logarithmic returns (volatility) of total volume at the 1-day time resolution for individual stocks as well as stock indices, and use Detrended Cross-Correlation Analysis (DCCA) to quantify the relation between price volatility and volume volatility.

5. A. M. Petersen, F. Wang, S. Havlin, H. E. Stanley.
   Quantitative law describing market dynamics before and after interest-rate change (pdf)
   Physical Review E 81, 066121 (2010). DOI: 10.1103/PhysRevE.81.066121
   
   We analyze the financial "earthquake" that occurs evey time the U.S. Federal Reserve makes an announcement to change the federal target interest rate, and estimate the magnitude of market `anticipation' and `surprise' using the fundamental relationship between the federal effective `overnight' interest rate and the 6-month Treasury Bill.
   
   Media coverage:
   - Bernanke Announcement Leaves Quake Like Aftershocks , Inside Science News Service

4. B. Podobnik, D. Horvatic, A. M. Petersen, M. Njavro, H. E. Stanley.
   Common scaling behavior in finance and macroeconomics (pdf)
   Eur. Phys. J. B 76, 487 (2010). DOI: 10.1140/epjb/e2009-00380-3
   
   We analyze the growth rates of worldwide stock indices and relate the market capitalization (MC) of the index to the gross domestic product (GDP) of the index country.
   

3. B. Podobnik, D. Horvatic, A. M. Petersen, H. E. Stanley.
   Quantitative relations between risk, return, and firm size (pdf)
   Europhysics Letters 85, 50003 (2009). DOI: 10.1209/0295-5075/85/50003
   
   For individual companies comprising the Nasdaq (2002-2008) and S&P500 (2003-2008) indices, we analyze the logarithmic growth rate (return) R of the stock price. We also relate the annual market capitalization (MC) and the return-to-risk < R >/sigma(R) for each company and find interesting differences between the Nasdaq and S&P500.

2. A. M. Petersen, W-S. Jung, H. E. Stanley.
   On the distribution of career longevity and the evolution of home run prowess in professional baseball (pdf)
   Europhysics Letters 83, 50010 (2008). DOI: 10.1209/0295-5075/83/50010
   
   How is it that 3% of all fielders finish their career with one at-bat and 3% of all pitchers finish their career with less than one inning pitched; Yet, there are also some careers that span more than 10,000 at-bats and 3,000 innings pitched? Analyzing every Major League Baseball player career over the 80-year period 1920-2000, we find a beautiful statistical law which describes both the extremely short careers of `one-hit wonders' as well as the extremely long careers of the `iron-horses'. Furthermore, analyzing home run rates, we find evidence consistent with performance enhancing drugs during the `Steroids Era' of the 1990's and 2000's.

1. M. Mobilia, A. Petersen, S. Redner.
   On the role of Zealotry in the Voter Model (pdf)
   J. Stat. Mech. 08, P08029 (2007). DOI: 10.1088/1742-5468/2007/08/P08029
   
   Why is it that in the history of democratic elections (e.g. Presidential elections), complete consensus (polarization) has never been achieved? For example, the largest percentage of voters for U.S. President elect was approximately 61% in Johnson over Goldwater, 1964. We investigate a stochastic opinion model in which consensus is stymied by the presence of zealots, agents who are completely fixed in their opinion, even if all their neighbors are of opposite opinion. Surprisingly, we find that the number and not the density of zealots determines the degree of consensus among the voters in our model.

Preprints:

Presentations: