National Bureau of Economic Research, Inc
NBER Working Papers
Postal: National Bureau of Economic Research, 1050 Massachusetts Avenue Cambridge, MA 02138, U.S.A.
Phone: 617-868-3900
Web page: http://www.nber.org
Email:
More information through EDIRC
Phone: 617-868-3900
Web page: http://www.nber.org
Email:
More information through EDIRC
For corrections or technical questions regarding this series, please contact ()
Series handle: repec:nbr:nberwo
Citations RSS feed: at CitEc
Top item:
Citations RSS feed: at CitEc
Impact factors
- Simple (last 10 years)
- Recursive (10)
- Discounted (10)
- Recursive discounted (10)
- H-Index (10)
- Aggregate (10)
Top item:
- By citations
- By downloads (last 12 months)
2003
- 9458 Time-Consistent No-Arbitrage Models of the Term Structure
by Michael W. Brandt & Amir Yaron - 9457 Gaucho Banking Redux
by Gerardo della Paolera & Alan M. Taylor - 9456 Inter-Asset Differences in Effective Estate Tax Burdens
by James Poterba & Scott Weisbenner - 9455 Simulating the Response to Reform of Canada's Income Security Programs
by Michael Baker & Jonathan Gruber & Kevin Milligan - 9454 The cash flow, return and risk characteristics of private equity
by Alexander Ljungqvist & Matthew Richardson - 9453 Portfolio Choice and Health Status
by Harvey S. Rosen & Stephen Wu - 9452 Omitted Product Attributes in Discrete Choice Models
by Amil Petrin & Kenneth Train - 9451 Letting States do the Dirty Work: State Responsibility for Federal Environmental Regulation
by Hilary Sigman - 9450 Regulation, Distribution Efficiency, and Retail Density
by David Flath - 9449 Testing Theories of Discrimination: Evidence from "Weakest Link"
by Steven D. Levitt - 9448 Legacies in Black and White: The Racial Composition of the Legacy Pool
by Cameron Howell & Sarah E. Turner - 9447 Distance, Skill Deepening and Development: Will Peripheral Countries Ever Get Rich?
by Stephen Redding & Peter K. Schott - 9446 Why Have Americans Become More Obese?
by David Cutler & Edward Glaeser & Jesse Shapiro - 9445 The Productivity of U.S. States Since 1880
by Kris James Mitchener & Ian W. McLean - 9444 Inefficiency of Corporate Investment and Distortion of Savings Behavior in Japan
by Albert Ando & Dimitrios Christelis & Tsutomu Miyagawa - 9443 The Response of the Informal Sector to Trade Liberalization
by Pinelopi K. Goldberg & Nina Pavcnik - 9442 Dynastic Management
by Francesco Caselli & Nicola Gennaioli - 9441 Tests of Multifactor Pricing Models, Volatility Bounds and Portfolio Performance
by Wayne E. Ferson - 9440 Routine
by Daniel S. Hamermesh - 9439 Export versus FDI
by Elhanan Helpman & Marc J. Melitz & Stephen R. Yeaple - 9438 Is Japan's Innovative Capacity in Decline?
by Lee Branstetter & Yoshiaki Nakamura - 9437 Hi-tech Innovation and Productivity Growth: Does Supply Create Its Own Demand?
by Robert J. Gordon - 9436 Mismeasurement of the CPI
by Kenn Ariga & Kenji Matsui - 9435 Economic Effects of Currency Unions
by Silvana Tenreyro & Robert J. Barro - 9434 The Price Impact and Survival of Irrational Traders
by Leonid Kogan & Stephen Ross & Jiang Wang & Mark Westerfield - 9433 How is Macro News Transmitted to Exchange Rates?
by Martin D. D. Evans & Richard K. Lyons - 9432 Corporate Investment with Financial Constraints: Sensitivity of Investment to Funds from Voluntary Asset Sales
by Gayane Hovakimian & Sheridan Titman - 9431 R&D and the Patent Premium
by Ashish Arora & Marco Ceccagnoli & Wesley M. Cohen - 9430 Optimal Policy with Partial Information in a Forward-Looking Model: Certainty-Equivalence Redux
by Lars E. O. Svensson & Michael Woodford - 9429 Work Costs and Nonconvex Preferences in the Estimation of Labor Supply Models
by Bradley T. Heim & Bruce D. Meyer - 9428 Cut to the Bone? Hospital Takeovers and Nurse Employment Contracts
by Janet Currie & Mehdi Farsi & W. Bentley MacLeod - 9427 Capital Account Liberalization and Growth: Was Mr. Mahathir Right?
by Barry Eichengreen & David Leblang - 9426 An Information-Based Trade Off Between Foreign Direct Investment and Foreign Portfolio Investment: Volatility, Transparency, and Welfare
by Itay Goldstein & Assaf Razin - 9425 The Costs of Wrongful-Discharge Laws
by David H. Autor & John J. Donohue III & Stewart J. Schwab - 9424 An Alternative Interpretation of the 'Resource Curse': Theory and Policy Implications
by Ricardo Hausmann & Roberto Rigobon - 9423 Limited Arbitrage and Short Sales Restrictions: Evidence from the Options Markets
by Eli Ofek & Matthew Richardson & Robert F. Whitelaw - 9422 How Do Markets Function? An Empirical Analysis of Gambling on the National Football League
by Steven D. Levitt - 9421 What is Wrong with Taylor Rules? Using Judgment in Monetary Policy through Targeting Rules
by Lars E. O. Svensson - 9420 Optimal Interest-Rate Rules: II. Applications
by Marc P. Giannoni & Michael Woodford - 9419 Optimal Interest-Rate Rules: I. General Theory
by Marc P. Giannoni & Michael Woodford - 9418 Another Look at the New York City School Voucher Experiment
by Alan B. Krueger & Pei Zhu - 9417 Foreign Firms and Indonesian Manufacturing Wages: An Analysis With Panel Data
by Robert E. Lipsey & Fredrik Sjoholm - 9416 Oligopoly Deregulation in General Equilibrium: A Tax Neutralization Result
by Gilbert E. Metcalf & George Norman - 9415 Oligopoly Deregulation and the Taxation of Commodities
by Gilbert E. Metcalf & George Norman - 9414 Catching Cheating Teachers: The Results of an Unusual Experiment in Implementing Theory
by Brian A. Jacob & Steven D. Levitt - 9413 Rotten Apples: An Investigation of the Prevalence and Predictors of Teacher Cheating
by Brian A. Jacob & Steven D. Levitt - 9412 Trading with the Unborn: A New Perspective on Capital Income Taxation
by Kent A. Smetters - 9411 Fractionalization
by Alberto Alesina & Arnaud Devleeschauwer & William Easterly & Sergio Kurlat & Romain Wacziarg - 9410 Pareto Improving Social Security Reform when Financial Markets are Incomplete?
by Dirk Krueger & Felix Kubler - 9409 Why Is There So Little Money in Politics?
by Stephen Ansolabehere & John M. de Figueiredo & James M. Snyder - 9408 Skill-specific rather then General Education: A Reason for US-Europe Growth Differences?
by Dirk Krueger & Krishna B. Kumar - 10623 How Have Borrowers Fared in Banking Mega-Mergers?
by Kenneth A. Carow & Edward J. Kane & Rajesh Narayanan - 10196 Optimal Policy with Low-Probability Extreme Events
by Lars E.O. Svensson - 10195 Escaping from a Liquidity Trap and Deflation: The Foolproof Way and Others
by Lars E.O. Svensson - 10194 Small Noise Asymptotics for a Stochastic Growth Model
by Noah Williams - 10193 Varieties of Currency Crises
by Graciela L. Kaminsky - 10192 Internal and External Labor Markets: A Personnel Economics Approach
by Edward P. Lazear & Paul Oyer - 10191 The Rise of the Skilled City
by Edward L. Glaeser & Albert Saiz - 10190 Why Firms Adopt Antitakeover Arrangements
by Lucian Arye Bebchuk - 10189 Optimal Integration Strategies for the Multinational Firm
by Gene M. Grossman & Elhanan Helpman & Adam Szeidl - 10188 Do Firms in Countries with Poor Protection of Investor Rights Hold More Cash?
by Lee Pinkowitz & Rene M. Stulz & Rohan Williamson - 10187 Menu Costs and Phillips Curves
by Mikhail Golosov & Robert E. Lucas - 10186 Stressed Out on Four Continents: Time Crunch or Yuppie Kvetch?
by Daniel S. Hamermesh & Jungmin Lee - 10185 What You Don't Know Can't Help You: Pension Knowledge and Retirement Decision Making
by Sewin Chan & Ann Huff Stevens - 10184 Risk Management, Capital Budgeting and Capital Structure Policy for Insurers and Reinsurers
by Kenneth A. Froot - 10183 The Invention of Inflation-Indexed Bonds in Early America
by Robert J. Shiller - 10182 The Size and Composition of Wealth Holdings in the United States, Italy, and the Netherlands
by Arie Kapteyn & Constantijn Panis - 10181 Assessing the Benefits to Developing Countries of Liberalization in Services Trade
by John Whalley - 10180 Choosing Between Peace and War
by Herschel I. Grossman - 10179 Assessing, Managing, and Financing Extreme Events: Dealing with Terrorism
by Howard Kunreuther & Erwann Michel-Kerjan & Beverly Porter - 10178 WTO Dispute Settlements in East Asia
by Dukgeun Ahn - 10177 Motivating Employee-Owners in ESOP Firms: Human Resource Policies and Company Performance
by Douglas Kruse & Richard Freeman & Joseph Blasi & Robert Buchele & Adria Scharf - 10176 How Do Electoral Rules Shape Party Structures, Government Coalitions, and Economic Policies?
by Torsten Persson & Gerard Roland & Guido Tabellini - 10175 Bargaining in the Shadow of the Law: Divorce Laws and Family Distress
by Betsey Stevenson & Justin Wolfers - 10174 Wages Equal Productivity: Fact or Fiction?
by Johannes Van Biesebroeck - 10173 The Impacts of an East Asia FTA on Foreign Trade in East Asia
by Shujiro Urata & Kozo Kiyota - 10172 The Effects of Financial Crises on International Trade
by Zihui Ma & Leonard Cheng - 10171 Gold, Fiat Money, and Price Stability
by Michael D. Bordo & Robert D. Dittmar & William T. Gavin - 10170 Consequences of Constitutions
by Torsten Persson - 10169 International R&D Deployment and Locational Advantage: A Case Study of Taiwan
by Meng-Chun Liu & Shin-Horng Chen - 10168 Competitive Liberalization and a US-SACU FTA
by John Whalley & J. Clark Leith - 10167 The Formation of International Production and Distribution Networks in East Asia
by Mitsuyo Ando & Fukinari Kimura - 10166 Reinventing Boston: 1640-2003
by Edward L. Glaeser - 10165 Institutions, Capital Constraints and Entrepreneurial Firm Dynamics: Evidence from Europe
by Mihir Desai & Paul Gompers & Josh Lerner - 10164 Does Human Capital Transfer from Parent to Child? The Intergenerational Effects of Compulsory Schooling
by Philip Oreopoulos & Marianne E. Page & Ann Huff Stevens - 10163 Helicopter Money: Irredeemable Fiat Money and the Liquidity Trap
by Willem H. Buiter - 10162 Remedies for Price Overcharges: The Deadweight Loss of Coupons and Discounts
by A. Mitchell Polinsky & Daniel L. Rubinfeld - 10161 Choosing the Federal Reserve Chair: Lessons from History
by Christina D. Romer & David H. Romer - 10160 The Trade and Investment Effects of Preferential Trading Arrangements
by Philippa Dee & Jyothi Gali - 10159 Estimating the Effects of Global Patent Protection in Pharmaceuticals: A Case Study of Quinolones in India
by Shubham Chaudhuri & Pinelopi K. Goldberg & Panle Jia - 10158 Governance and Bank Valuation
by Gerard Caprio & Luc Laeven & Ross Levine - 10157 The Risk Tolerance of International Investors
by Kenneth A. Froot & Paul G. J. O'Connell - 10156 The Effects of Overseas Investment on Domestic Employment
by Tain-Jy Chen & Ying-Hua Ku - 10155 Do Dropouts Drop Out Too Soon? International Evidence From Changes in School-Leaving Laws
by Philip Oreopoulos - 10154 Common Sense and Simplicity in Empirical Industrial Organization
by Ariel Pakes - 10153 The Character and Determinants of Corporate Capital Gains
by Mihir Desai & William M. Gentry - 10152 Trade Liberalization and Growth: New Evidence
by Romain Wacziarg & Karen Horn Welch - 10151 Commitment Vs. Flexibility
by Manuel Amador & Ivan Werning & George-Marios Angeletos - 10150 Corporate Earnings Track the Competitive Benchmark
by Robert E. Hall - 10149 Optimal Fiscal and Monetary Policy Under Imperfect Competition
by Stephanie Schmitt-Grohe & Martin Uribe - 10148 The Effect of Word of Mouth on Sales: Online Book Reviews
by Judith A. Chevalier & Dina Mayzlin - 10147 International Determinants of Religiosity
by Robert Barro & Rachel M. McCleary - 10146 Estimating Models of On-the-Job Search Using Record Statistics
by Gadi Barlevy - 10145 Which Countries Export FDI, and How Much?
by Assaf Razin & Yona Rubinstein & Efraim Sadka - 10144 Endogenous Financial Openness: Efficiency and Political Economy Considerations
by Joshua Aizenman & Ilan Noy - 10143 Liberalization in China's Key Service Sectors Following WTO Accession: Some Scenarios and Issues of Measurement
by John Whalley - 10142 Agents of Embeddedness
by Pierre Azoulay - 10141 Weather Forecasting for Weather Derivatives
by Sean D. Campbell & Francis X. Diebold - 10140 The Two-Part Instrument in a Second-Best World
by Don Fullerton & Ann Wolverton - 10139 A Simulation-Based Welfare Loss Calculation for Labor Taxes with Piecewise-Linear Budgets
by Don Fullerton & Li Gan - 10138 Regeneration, Labour Supply and the Welfare Costs of Taxes
by Edgar Cudmore & John Whalley - 10137 The Use of Literature Based Elasticity Estimates in Calibrated Models of Trade-Wage Decompositions: A Calibmetric Approach
by Hui Huang & John Whalley - 10136 Kleptocracy and Divide-and-Rule: A Model of Personal Rule
by Daron Acemoglu & James A. Robinson & Thierry Verdier - 10135 Competitive Risk Sharing Contracts with One-Sided Commitment
by Dirk Krueger & Harald Uhlig - 10134 Does Child Labor Decline with Improving Economic Status?
by Eric V. Edmonds - 10133 Entrant Experience and Plant Exit
by Timothy Dunne & Shawn D. Klimek & Mark J. Roberts - 10132 Aggregate Consequences of Limited Contract Enforceability
by Thomas Cooley & Ramon Marimon & Vincenzo Quadrini - 10131 The Price is (Almost) Right
by Randolph B. Cohen & Christopher Polk & Tuomo Vuolteenaho - 10130 Have National Business Cycles Become More Synchronized?
by Michael D. Bordo & Thomas Helbling - 10129 Law and Employment: Lessons from Latin America and the Caribbean
by James Heckman & Carmen Pages - 10128 External Constraints on Monetary Policy and the Financial Accelerator
by Mark Gertler & Simon Gilchrist & Fabio Natalucci - 10127 Health Plan Conversions: Are They in the Public Interest?
by Nancy Dean Beaulieu - 10126 Legal Institutions and Financial Development
by Thorsten Beck & Ross Levine - 10125 International Lending of Last Resort and Moral Hazard: A Model of IMF's Catalytic Finance
by Giancarlo Corsetti & Bernardo Guimaraes & Nouriel Roubini - 10124 Why is Manhattan So Expensive? Regulation and the Rise in House Prices
by Edward L. Glaeser & Joseph Gyourko & Raven Saks - 10123 The LM Curve: A Not-So-Fond Farewell
by Benjamin Friedman - 10122 The Timing of Births: Is the Health of Infants Counter-Cyclical?
by Rajeev Dehejia & Adriana Lleras-Muney - 10121 What Mean Impacts Miss: Distributional Effects of Welfare Reform Experiments
by Marianne Bitler & Jonah Gelbach & Hilary Hoynes - 10120 Behavioral Decision-Making: An Application to the Setting of Magazine Subscription Prices
by Fiona Scott Morton & Sharon Oster - 10119 Pareto Efficient Income Taxation with Stochastic Abilities
by Marco Battaglini & Stephen Coate - 10118 The Central Role of Noise in Evaluating Interventions that Use Test Scores to Rank Schools
by Kenneth Y. Chay & Patrick J. McEwan & Miguel Urquiola - 10117 A Multiple Indicators Model for Volatility Using Intra-Daily Data
by Robert F. Engle & Giampiero M. Gallo - 10116 Two Trees: Asset Price Dynamics Induced by Market Clearing
by John H. Cochrane & Francis A. Longstaff & Pedro Santa-Clara - 10115 Cross-Border Valuation: The International Cost of Equity Capital
by Gordon M. Bodnar & Bernard Dumas & Richard D. Marston - 10114 Patents and R&D as Real Options
by Eduardo S. Schwartz - 10113 The Effect of School Choice on Student Outcomes: Evidence from Randomized Lotteries
by Julie Berry Cullen & Brian A. Jacob & Steven Levitt - 10112 Financial Aid and Students' College Decisions: Evidence from the District of Columbia's Tuition Assistance Grant Program
by Katharine Abraham & Melissa A. Clark - 10111 A Tale of Two Time Scales: Determining Integrated Volatility with Noisy High Frequency Data
by Lan Zhang & Per A. Mykland & Yacine Ait-Sahalia - 10110 Cross-Border Tax Externalities: Are Budget Deficits Too Small?
by Willem Buiter & Anne C. Sibert - 10109 The Optimal Degree of Discretion in Monetary Policy
by Susan Athey & Andrew Atkeson & Patrick Kehoe - 10108 The Market for American State Government Bonds in Britain and the United States, 1830-1843
by Namsuk Kim & John Joseph Wallis - 10107 Generalized Disappointment Aversion and Asset Prices
by Bryan R. Routledge & Stanley E. Zin - 10106 Firm Location and the Creation and Utilization of Human Capital
by Andres Almazan & Adolfo de Motta & Sheridan Titman - 10105 Nonparametric Tests for Common Values at First-Price Sealed-Bid Auctions
by Philip A. Haile & Han Hong & Matthew Shum - 10104 Categorical Redistribution in Winner-Take-All Markets
by Roland G. Fryer & Glenn C. Loury - 10103 Color-Blind Affirmative Action
by Roland Fryer & Glenn C. Loury & Tolga Yuret - 10102 Self Enforcing Voting in International Organizations
by Giovanni Maggi & Massimo Morelli - 10101 Stakeholder, Transparency and Capital Structure
by Andres Almazan & Javier Suarez & Sheridan Titman - 10100 The Role of Retiree Health Insurance in the Employment Behavior of Older Men
by David M. Blau & Donna B. Gilleskie - 10099 Optimal Taxation When Consumers Have Endogenous Benchmark Levels of Consumption
by Andrew B. Abel - 10098 Grasshoppers, Ants, and Pre-Retirement Wealth: A Test of Permanent Income
by Erik Hurst - 10097 How Do Legal Differences and Learning Affect Financial Contracts?
by Steven N. Kaplan & Frederic Martel & Per Stromberg - 10096 The Developed World's Demographic Transition - The Roles of Capital Flows, Immigration, and Policy
by Hans Fehr & Sabine Jokisch & Laurence Kotlikoff - 10095 Crisis Resolution: Next Steps
by Barry Eichengreen & Kenneth Kletzer - 10094 On the Writing and the Interpretation of Contracts
by Steven Shavell - 10093 Monetary Policies for Developing Countries: The Role of Corruption
by Haizhou Huang & Shang-Jin Wei - 10092 Health Insurance Coverage and the Macroeconomy
by John Cawley & Kosali I. Simon - 10091 Getting Inside the "Black Box" of Head Start Quality: What Matters and What Doesn't?
by Janet Currie & Matthew Neidell - 10090 The Environment and Globalization
by Jeffrey A. Frankel - 10089 An "Inflation Reports" Report
by Eric Leeper - 10088 Child Labor, Crop Shocks, and Credit Constraints
by Kathleen Beegle & Rajeev Dehejia & Roberta Gatti - 10087 Inequality and Trade
by Devashish Mitra & Vitor Trindade - 10086 Does the Failure of the Expectations Hypothesis Matter for Long-Term Investors
by Antonios Sangvinatsos & Jessica A. Wachter - 10085 The Impact on Consumption and Saving of Current and Future Fiscal Policies
by Katherine Grace Carman & Jagadeesh Gokhale & Laurence J. Kotlikoff - 10084 Labor Versus Capital in Trade-Policy Determination: The Role of General-Interest and Special-Interest Politics
by Pushan Dutt & Devashish Mitra - 10083 Acquiring Knowledge Within and Across Firm Boundaries: Evidence from Clinical Development
by Pierre Azoulay - 10082 Global Sourcing
by Pol Antràs & Elhanan Helpman - 10081 Zvi Griliches' Contribution to the Theory of Human Capital
by Reuben Gronau - 10080 How do Regimes Affect Asset Allocation?
by Andrew Ang & Geert Bekaert - 10079 A Theory of Factor Allocation and Plant Size
by Thomas J. Holmes & Matthew F. Mitchell - 10078 Inventories and the Business Cycle: An Equilibrium Analysis of (S,s) Policies
by Aubhik Khan & Julia Thomas - 10077 Determinants of Labor Demand in Colombia: 1976-1996
by Mauricio Cardenas & Raquel Bernal - 10076 Economic Insights from Internet Auctions: A Survey
by Patrick Bajari & Ali Hortacsu - 10075 Mass Secondary Schooling and the State
by Claudia Goldin & Lawrence Katz - 10074 A Prism into the PPP Puzzles: The Micro-foundations of Big Mac Real Exchange Rates
by David C. Parsley & Shang-Jin Wei - 10073 Crises and Growth: A Re-Evaluation
by Romaine Ranciere & Aaron Tornell & Frank Westermann - 10072 The Alternative Minimum Tax and Effective Marginal Tax Rates
by Daniel Feenberg & James Poterba - 10071 Liquidity Shortages and Banking Crises
by Douglas W. Diamond & Raghuram G. Rajan - 10070 Money in a Theory of Banking
by Douglas W. Diamond & Raghuram G. Rajan - 10069 The Origins of Spatial Interaction
by Wolfgang Keller & Carol H. Shiue - 10068 Labor Market Discrimination and Racial Differences in Premarket Factors
by Pedro Carneiro & James J. Heckman & Dimitriy V. Masterov - 10067 Globalizing Activities and the Rate of Survival: Panel Data Analysis on Japanese Firms
by Fukunari Kimura & Takamune Fujii - 10066 Why the Apple Doesn't Fall Far: Understanding Intergenerational Transmission of Human Capital
by Sandra E. Black & Paul J. Devereux & Kjell G. Salvanes - 10065 Revisiting Some Productivity Debates
by Johannes Van Biesebroeck - 10064 Domestic Capital Market Reform and Access to Global Finance: Making Markets Work
by Peter Blair Henry & Peter Lombard Lorentzen - 10063 Consequences and Predictors of New Health Events
by James P. Smith - 10062 Benefit Plan Design and Prescription Drug Utilization Among Asthmatics: Do Patient Copayments Matter?
by William H. Crown & Ernst R. Berndt & Onur Baser & Stan N. Finkelstein & Whitney P. Witt - 10061 The Unholy Trinity of Financial Contagion
by Graciela L. Kaminsky & Carmen Reinhart & Carlos A. Vegh - 10060 School-to-Career Programs and Transitions to Employment and Higher Education
by David Neumark & Donna Rothstein - 10059 Efficiency Costs of Meeting Industry-Distributional Constraints under Environmental Permits and Taxes
by A.L. Bovenberg & Lawrence H. Goulder & Derek J. Gurney - 10058 Is Japan's Trade (still) Different?
by James Harrigan & Rohit Vanjani - 10057 A Normal Country
by Andrei Shleifer & Daniel Treisman - 10056 The Demand for Coordination
by Wouter Dessein & Tano Santos - 10055 Small Farms, Externalities, and the Dust Bowl of the 1930's
by Zeynep K. Hansen & Gary D. Libecap - 10054 Corporate Earnings and the Equity Premium
by Francis Longstaff & Monika Piazzesi - 10053 Air Quality, Infant Mortality, and the Clean Air Act of 1970
by Kenneth Y. Chay & Michael Greenstone - 10052 Heterogeneity and the FDI versus Export Decision of Japanese Manufacturers
by Keith Head & John Ries - 10051 Winners and Losers of Tax Competition in the European Union
by Enrique G. Mendoza & Linda L. Tesar - 10050 Growth Strategies
by Dani Rodrik - 10049 Product Substitutability and Productivity Dispersion
by Chad Syverson