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585 results on '"Sethi, Rajiv"'

3. The Dynamics of Leverage and the Belief Distribution of Wealth

Author

Datta, Bikramaditya and Sethi, Rajiv

Subjects
Economics - General Economics
Abstract

The scale and terms of aggregate borrowing in an economy depend on the manner in which wealth is distributed across potential creditors with heterogeneous beliefs about the future. This distribution evolves over time as uncertainty is resolved, in favour of optimists if loans are repaid in full, and in favour of pessimists if there is widespread default. We model this process in an economy with two assets - risky bonds and risk-free cash. Within periods, given the inherited distribution of wealth across belief types, the scale and terms of borrowing are endogenously determined. Following good states, aggregate borrowing and the face value of debt both rise, and the interest rate falls. In the absence of noise, wealth converges to beliefs that differ systematically from the objective probability governing state realisations, with greater risk-aversion associated with greater optimism. In the presence of noise, the economy exhibits periods of high performance, punctuated by periods of crisis and stagnation.

Published
2023

5. Randomized Trial of Augmented Pelvic Fixation in Patients Undergoing Thoracolumbar Fusion for Adult Spine Deformity: Initial Results from a Multicenter Randomized Trial

Author

Mundis, Gregory, Herzog, Joshua, Buchholz, Avery, Eastlack, Robert, Elder, Benjamin, Lieberman, Isador, Kim, Han Jo, Matheus, Virgilio, Snowden, Ryan, Franke, Jorg, Klapproth, Lars, Leveque, Jean-Christophe, Sembrano, Jonathan, Arakal, Raj, Chapman, Matt, Khan, Safdar, Lee, Robert, Belanger, Theodore, Wong, Cyrus, Ajayi, Olaide, Kazemi, Noojan, Park, Paul, Singla, Anuj, Buckland, Aaron, Hah, Raymond, Khalil, Jad, Kleck, Christopher, Mokawem, Michael, Nemani, Venu, Turner, Jay, Colman, Matt, Hirschl, Robert, Kent, Roland, Kuhns, Craig, Prestamburgo, Domenico, Sethi, Rajiv, Smith, Gregory, Uribe, Juan, Cress, Marshall C., Dewald, Christopher, Fogelson, Jeremy, Martin, Chris, Meiler, Katherine, Mullin, Jeffrey, Oppenlander, Mark, Ou-Yang, David, Phillips, Frank, Polly, David, Mundis, Greg, Leveque, Jean-Christopher, Elder, Benjamin D., Martin, Christopher, and Shaffrey, Christopher

Published
2024
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7. Models, Markets, and the Forecasting of Elections

Author

Sethi, Rajiv, Seager, Julie, Cai, Emily, Benjamin, Daniel M., and Morstatter, Fred

Subjects
Economics - General Economics, Computer Science - Computers and Society
Abstract

We examine probabilistic forecasts for battleground states in the 2020 US presidential election, using daily data from two sources over seven months: a model published by The Economist, and prices from the PredictIt exchange. We find systematic differences in accuracy over time, with markets performing better several months before the election, and the model performing better as the election approached. A simple average of the two forecasts performs better than either one of them overall, even though no average can outperform both component forecasts for any given state-date pair. This effect arises because the model and the market make different kinds of errors in different states: the model was confidently wrong in some cases, while the market was excessively uncertain in others. We conclude that there is value in using hybrid forecasting methods, and propose a market design that incorporates model forecasts via a trading bot to generate synthetic predictions. We also propose and conduct a profitability test that can be used as a novel criterion for the evaluation of forecasting performance.

Published
2021

21. Does Pedicle Morphology Affect the Safety and Accuracy of Pedicle Screw Placement Using 3D-Printed Guides? A 5-Year, Single-Center Experience With 2210 Screws Placed for Adult Spinal Deformity Reconstruction.

Author

KUMAR, RAKESH, LEVEQUE, JEAN-CHRISTOPHE, LOUIE, PHILIP K., SETHI, RAJIV, and NEMANI, VENU M.

Subjects
COMPUTER-aided design software, SPINE abnormalities, COMPUTED tomography, IDIOPATHIC diseases, SCREWS, FLUOROSCOPY
Abstract

Background: Adult spinal deformity (ASD) surgery often involves the placement of pedicle screws using various methods, including freehand technique, fluoroscopic guidance, and computer-assisted intraoperative navigation, each with distinct limitations. Particularly challenging is the instrumentation of pedicles with small or absent cancellous channels (Watanabe types C and D pedicles), commonly found at the apex of large curves where precise screw placement is crucial for effective deformity correction. 3D-printed pedicle screw drill guides (3DPSG) may assist in accurately placing pedicle screws while minimally disrupting the standard ASD surgery workflow. This study aims to evaluate the safety and efficacy of 3DPSG in ASD patients with Watanabe types C and D pedicles, where the safe corridor for screw placement is limited. Methods: 3DPSG were designed using fine cut (=1.25 mm) computed tomography scans. Preoperative screw trajectory planning and guide manufacturing were conducted using computer-aided design software (Mighty Oak Medical, Englewood, CO). Four ASD surgeons with varying experience levels placed the guides. Data on patient demographics, pedicle morphology, number of levels instrumented, and implant-related complications were collected. Results: The study included 115 patients (median age 67, range 18-81 years) with 2210 screws placed from T1 to L5. The median number of levels instrumented per case was 11 (range 7-12). Diagnoses included adult degenerative scoliosis (n = 62), adult idiopathic scoliosis (n = 30), Scheuermann's kyphosis (n = 2), and other complex conditions (n = 21). The overall accuracy rate for pedicle screw placement was 99.5%, with a 0% malposition rate in type C and D pedicles. No vascular or neurological complications or reoperations related to screw placement were reported. Conclusion: 3DPSG facilitates safe and accurate pedicle screw placement regardless of pedicle morphology in ASD surgeries. This includes the challenging Watanabe types C and D pedicles, typically found at curve apices, enabling surgeons to achieve high implant density and optimal spinal fixation in ASD patients. [ABSTRACT FROM AUTHOR]

Published
2024
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26. Inside Money, Procyclical Leverage, and Banking Catastrophes

Author

Brummitt, Charles D., Sethi, Rajiv, and Watts, Duncan J.

Subjects
Quantitative Finance - Pricing of Securities, Quantitative Finance - General Finance, Quantitative Finance - Risk Management
Abstract

We explore a model of the interaction between banks and outside investors in which the ability of banks to issue inside money (short-term liabilities believed to be convertible into currency at par) can generate a collapse in asset prices and widespread bank insolvency. The banks and investors share a common belief about the future value of certain long-term assets, but they have different objective functions; changes to this common belief result in portfolio adjustments and trade. Positive belief shocks induce banks to buy risky assets from investors, and the banks finance those purchases by issuing new short-term liabilities. Negative belief shocks induce banks to sell assets in order to reduce their chance of insolvency to a tolerably low level, and they supply more assets at lower prices, which can result in multiple market-clearing prices. A sufficiently severe negative shock causes the set of equilibrium prices to contract (in a manner given by a cusp catastrophe), causing prices to plummet discontinuously and banks to become insolvent. Successive positive and negative shocks of equal magnitude do not cancel; rather, a banking catastrophe can occur even if beliefs simply return to their initial state. Capital requirements can prevent crises by curtailing the expansion of balance sheets when beliefs become more optimistic, but they can also force larger price declines. Emergency asset price supports can be understood as attempts by a central bank to coordinate expectations on an equilibrium with solvency., Comment: 31 pages, 10 figures

Published
2014
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