The UCSD Economics PhD program is one of best economics PhD programs. I post its admission requirement here for easier discussion.

Here is the link: http://economics.ucsd.edu/grad/gradAdm/admFaqs.php
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MASTER'S DEGREE, PH.D. DEGREE

• Do you offer a Master’s Degree?
  No. The Department does not enroll students who seek a Master’s degree as a terminal degree.
• Do you offer a Ph.D. in Finance?
  We do not offer a Ph.D. in Finance.  We offer a Ph.D. in Economics.  If you are interested in an MBA or Ph.D. in Management, you should contact the Rady School of Management.
• I am currently enrolled in a Master’s program in Economics and would like to know if it would be possible to transfer some credits to shorten the Ph.D. program to about three years?
  No.  It is not possible to transfer credits into our program; however, if you are admitted into the program, you may take the qualifying exam in August or September (date to be determined).  If you pass the qualifying exams, you would not need to complete the applicable core course work but you may still be required to take some of the electives (to fulfill field course requirements and required number of electives).
  

TRANSCRIPTS

• How should I submit transcripts?
  Please do not send hard copies of your transcripts at this time. You may upload your unofficial transcripts to the online application. We will only require official, hard copies of your transcripts if admitted and you decide to attend UC San Diego. For international students, please make sure to upload a translated copy of your transcripts.
  

GRE/TOEFL

• What is your policy on GRE retakes?
  Regarding GRE retakes, your highest scores will be considered of any test scores that are received before the admission application deadline.  Remember that official scores from ETS are required.  Copies are not accepted.  Official scores must be received either by mail (postmark or carrier sent date) or electronically by the application deadline in order to be considered “on time.”
• I am a foreign student but completed my undergraduate studies at an English speaking university outside of the United States.   Do I still need to provide TOEFL scores?
  The Test of English as a Foreign Language (TOEFL) or International English Language Testing System (IELTS) is required for international applicants whose native language is not English and who have not studied full-time for one uninterrupted year at a university-level institution in a country where English is the official language.
• My current GRE scores are 7 years old.  Will they be accepted?
  GRE scores cannot be more than 5 years old.  TOEFL scores cannot be more than 2 years old. If GRE scores exceed the 5 year-old mark or TOEFL scores the 2 year-old mark, they would need to be retaken in order to be accepted.
• Do you accept the GMAT in place of the GRE?
  No.  The GRE is required and cannot be replaced with the GMAT.
• Do you require the GRE Economics Subject Test?
  No. We do not.
• What is your department code for the GRE and TOEFL?
  Our department code for the GRE is 1801 and for the TOEFL it is 84. UCSD's institution code for the GRE/TOEFL is 4836.
  

GPA REQUIREMENTS

• I am a foreign student and my university does not have a system of GPA.  How would the absence of a “GPA” be evaluated?
  If your university does not have a system of GPA, then we will look at the transcripts and determine if you meet the criteria for review.
• I am planning to apply to your graduate program in economics, but unfortunately, my GPA is below the 3.5 minimum.  Since I do not make the cutoff with my 3.35, should I bother submitting an application?Your GPA is just below the minimum required for consideration, but if the remainder of your supporting materials are strong (e.g., GRE and letters of recommendation), there is the possibility that your application would be reviewed.  As to whether this contingency would justify submitting your application, this would be a judgment call on your part.
• Regarding final transcripts for spring courses, since your application deadline is in January, how and when do I submit final grades for spring classes?
  If admitted, you should submit transcripts for as much completed work as possible.  Your admission status will be considered “provisional” until those transcripts are submitted along with confirmation of your degree conferral. Should you accept our offer of admission, "provisional" status would not preclude your ability to register for the Fall quarter.
  

MATH & ECONOMICS COURSE PREPARATION

• Regarding math preparation for your program, are there any advanced calculus courses I must take to be able to qualify as a potential Ph.D. candidate?
  All applicants must have a minimum of one year of college-level calculus.  However, one year is likely to be inadequate background for the first year of core classes.  Students are therefore encouraged to complete courses in vector calculus, differential equations, linear algebra and mathematical analysis prior to the start of graduate school.
• I have an undergraduate degree in Psychology and although I have a strong math background, I am concerned about whether I have an adequate background in Economics.
  Those whose background in economics is not strong are urged to review microeconomics and macroeconomics at the upper division level.
  

ADMISSION STATISTICS

• How many students do you accept into your Ph.D. program each year?
  In general, we receive between 500 and 600 applications per year, and admit about 20% of them.  Our incoming classes are on the average 25 students.
• How are applications evaluated?
  Admission is based on an overall assessment of a candidate’s interests, background and potential.  The composition of the applicant pool differs from year to year.  For these reasons it is difficult to provide a definitive formula for admissibility.
  

FINANCIAL AID

• If I were admitted, what are my chances of getting financial aid?
  First Year Students:  Admission and financial aid awards are based on an overall assessment of a candidate’s interest, background and potential, and whether they are domestic or foreign.  Furthermore, admission rates and financial aid awards will depend on the applicant pool, which differs from year to year.  Approximately 75% of admits are offered a first-year financial aid package (e.g., teaching assistantships, tuition & fee scholarships, fellowships).  
  Second Year through Fifth Year Students:  Any full-time student making solid progress in the program is assured of at least partial aid during the second through fifth years.
• If admitted and not offered first year funding from the department, where would I get information about outside funding?
  Check out the Office of Graduate Studies’ Information on Fellowships and Traineeships.  It contains links to comprehensive funding databases, grant writing guides and selected funding opportunities available only to UCSD graduate students.
  

LETTERS OF RECOMMENDATION

• What kind of letters of recommendation are preferred, particularly if potential recommenders come from a combination of professional and academic sources?
  Letters of recommendation should come from recommenders who can speak to your academic skills as well as the kind of skills that would make you a dedicated, focused student.  It is your choice which letters you think would support your chances for acceptance into graduate school.
  

SUPPLEMENTARY MATERIALS

• Does the department encourage/appreciate an academic writing sample included with the supporting materials required for admission?
  You are welcome to submit a writing sample, although it is not required.  Many applicants have included them as a supplement to their application materials.  Any writing sample you would like to include as supporting documentation will be included in your file, along with all required materials, when your completed admissions packet is presented for review. Only PDF versions of writing samples will be accepted, uploaded to the online application under the "optional document submission" page.
  

JOB MARKET PLACEMENT

• Could you give me information on placements in the last couple of years for graduating Ph.D. students in your department?
  Check out the department’s active, successful Job Market program for its Ph.D. graduates.