Peer-Reviewed Publications

Fragmentation and Inefficiencies in the U.S. Equity Markets: Evidence from the Dow 30

Brian F. Tivnan, David Rushing Dewhurst, Colin M. Van Oort, John H. Ring IV, Tyler J. Gray, Brendan F. Tivnan, Matthew T. K. Koehler, Matthew T. McMahon, David Slater, Jason Veneman, Christopher M. Danforth
PLOS ONE 15(1): e0226968 (January 2020)

NMS depiction
The National Market System, colloquially known as the "stock market" is more complex than many realize. The image is Figure 3 from "Fragmentation and Inefficiencies in the U.S. Equity Markets: Evidence from the Dow 30".

Using the most comprehensive source of commercially available data on the US National Market System, we analyze all quotes and trades associated with Dow 30 stocks in 2016 from the vantage point of a single and fixed frame of reference. Contrary to prevailing academic and popular opinion, we find that inefficiencies created in part by the fragmentation of the equity market place are widespread and potentially generate substantial profit for agents with superior market access. Information feeds reported different prices for the same equity, violating the commonly-supposed economic behavior of a unified price for an indistinguishable product more than 120 million times, with “actionable” dislocation segments totaling almost 64 million. During this period, roughly 22% of all trades occurred while the SIP and aggregated direct feeds were dislocated. The current market configuration resulted in a realized opportunity cost totaling over $160 million when compared with a single feed, single exchange alternative a conservative estimate that does not take into account intra-day offsetting events.

Connected graphs with a given degree sequence: efficient sampling, correlations, community detection and robustness

John H. Ring IV, Jean-Gabriel Young, Laurent Hébert-Dufresne
Proceedings of NetSci-X 2020

modularity maximization
Figure 4 from publication. Outcome of modularity maximization on the Norwegian board of directors network.

Random graph models can help us assess the significance of the structural properties of real complex systems. Given the value of a graph property and its value in a randomized ensemble, we can determine whether the property is explained by chance by comparing its real value to its value in the ensemble. The conclusions drawn with this approach obviously depend on the choice of randomization. We argue that keeping graphs in one connected piece, or component, is key for many applications where complex graphs are assumed to be connected either by definition (e.g. the Internet) or by construction (e.g. a crawled subset of the World-Wide Web obtained only by following hyperlinks). Using an heuristic to quickly sample the ensemble of small connected simple graphs with a fixed degree sequence, we investigate the significance of the structural patterns found in real connected graphs. We find that, in sparse networks, the connectedness constraint changes degree correlations, the outcome of community detection with modularity, and the predictions of percolation on the ensemble.

Proof-Carrying Network Code

Christian Skalka, John H. Ring IV, David Darias, Minseok Kwon, Sahil Gupta, Kyle Diller, Steffen Smolka, Nate Foster
Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security

IoT testbed
Figure 9 from publication. Real network testbed with a Fitbit Charge 3 for sleep tracking and an iHealth Feel wireless blood pressure monitor.

Computer networks often serve as the first line of defense against malicious attacks. Although there are a growing number of tools for defining and enforcing security policies in software-defined networks (SDNs), most assume a single point of control and are unable to handle the challenges that arise in networks with multiple administrative domains. For example, consumers may want want to allow their home IoT networks to be configured by device vendors, which raises security and privacy concerns. In this paper we propose a framework called Proof-Carrying Network Code (PCNC) for specifying and enforcing security in SDNs with interacting administrative domains. Like Proof-Carrying Authorization (PCA), PCNC provides methods for managing authorization domains, and like Proof-Carrying Code (PCC), PCNC provides methods for enforcing behavioral properties of network programs. We develop theoretical foundations for PCNC and evaluate it in simulated and real network settings, including a case study that considers security in IoT networks for home health monitoring.


Scaling of inefficiencies in the U.S. equity markets: Evidence from three market indices and more than 2900 securities

February 2019 by David Rushing Dewhurst, Colin M. Van Oort, John H. Ring IV, Tyler J. Gray, Christopher M. Danforth, Brian F. Tivnan

GALE Dislocations
Figure 3 from publication. Dislocation segments in GALE from July 2016 to June 2017 are plotted in real-time, modulo day. Note the non-uniform density, where a large number of dislocation segments occur near the beginning of the trading day.

Using the most comprehensive, commercially-available dataset of trading activity in U.S. equity markets, we catalog and analyze dislocation segments and realized opportunity costs(ROC) incurred by market participants. We find that dislocation segments are common, observing a total of over 3.1 billion dislocation segments in the Russell 3000 during trading in 2016, or roughly 525 per second of trading. Up to 23% of observed trades may have contributed the the measured inefficiencies, leading to a ROC greater than $2 billion USD. A subset of the constituents of the S&P 500 index experience the greatest amount of ROC and may drive inefficiencies in other stocks. In addition, we identify fine structure and self-similarity in the intra-day distribution of dislocation segment start times. These results point to universal underlying market mechanisms arising from the physical structure of the U.S. National Market System.