Talk:Lead–lag effect

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message: Economics
A lead-lag effect, in economics, describes the situation where one (leading) variable is correlated with the values of another (lagging) variable at later times.  
For example, economists have found that in some circumstances there is a lead-lag effect between large-capitalization and small-capitalization stock-portfolio prices (Lo and MacKinlay, 1990).
References
* Andrew W. Lo and A. Craig MacKinlay, "When are contrarian profits due to stock market overreaction," Review of Financial Studies 3 (2), 175-205 (1990).
* "The fuzzy logic between lead and lag indicators". Business Management Issue.
* Hou, Kewei, "Industry Information Diffusion and the Lead-Lag Effect in Stock Returns". Ohio State University - Fisher College of Business.
Engineering
Main article: Phase
In engineering, the lead-lag effect is the transfer function of two or more variables, which is based on the ordinary differential equation. The two body equation is defined as:
			
a_0 y + a_1 {dy \over dt} = b_0 x + b_1 {dx \over dt}
where  a_0, a_1, b_0,  and  b_1  are constants.
This coupling effect is symmetrical irrespective of directionality. In assessing the "frequency" of the oscillations, amplitude and phase may be different. One frequency may lead ahead or lag behind another frequency. The lead time constant can be greater than the lag time constant producing "time lead" [or pontentiality].
Symmetrical dynamic relations make periodic input oscillations so that the output has the same phase as the input. Lead-lag effects concern two-body problems, three-body problems, and multi-body problems. A lag (or delay) and a lead (or draw) is a phase gradient. 	
References
* "Phase, Group, and Signal Velocity".  MathPages.
* "Lead-Lag Frequency Response". MathPages.
* "Frequency Response of First-Order Lag". MathPages.
* "Lead-Lag Compensation". Experiment 4. ECE 409 Lab Manual.
See also
* Lead-lag compensator
* Phasor
* Group (mathematics)
* Signal velocity
* Polyphase system
* Harmonic oscillator
* RLC series circuit
--J. D. Redding 11:36, 12 August 2013 (UTC)
thread_title:  this needs to be incorporated into the aticle