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  • Pre and Post portfolio formation returns

    Dear Statalist members,

    Currently, I have a large panel dataset with monthly returns and 5 portfolio's based on the company's R&D expenditures scaled by market cap. The portfolio's are formed on a yearly basis in June.
    Now, I want to perform a similar analysis as Louis K. C. Chan, Josef Lakonishok, Theodore Sougiannis (2001) The Stock Market Valuation of Research and Development Expenditures (wiley.com)
    and calculate each portfolio’s average annual buy-and-hold return over the five years prior to portfolio formation; over each year from one to three years after portfolio formation; and averaged over the three post formation years.

    I have been searching through Statalist and haven't been able to find a fitting solution.
    I used the following code to calculate the average yearly returns from July to June:

    Code:
    bys gvkey functional_year: asrol usret, s(product) add(1)
    A sample of my dataset is given below:
    usret are the monthly returns and functional_year are adjusted years in order to create portfolio's in June.

    Code:
    * Example generated by -dataex-. For more info, type help dataex
    clear
    input long gvkey float(monthly_date functional_year usret) int portfolio
    1166 480 1999    .09326574 .
    1166 481 1999    .24016953 .
    1166 482 1999   -.03944441 .
    1166 483 1999    .09743556 .
    1166 484 1999   -.18024014 .
    1166 485 1999   -.02928259 4
    1166 486 2000  .0041769478 4
    1166 487 2000   -.03308512 4
    1166 488 2000    -.3078191 4
    1166 489 2000   -.08736072 4
    1166 490 2000   -.25651398 4
    1166 491 2000    -.1653086 4
    1166 492 2000       .83484 4
    1166 493 2000   -.23410656 4
    1166 494 2000    .25346023 4
    1166 495 2000    .28960082 4
    1166 496 2000   -.03155282 4
    1166 497 2000   -.10982657 4
    1166 498 2001     .1799191 4
    1166 499 2001   -.07481738 4
    1166 500 2001    -.4534363 4
    1166 501 2001     .3561824 4
    1166 502 2001   -.04567805 4
    1166 503 2001    .26718995 4
    1166 504 2001   -.04475289 4
    1166 505 2001    .16981766 4
    1166 506 2001    .20963725 4
    1166 507 2001   -.09086589 4
    1166 508 2001    -.1571756 4
    1166 509 2001   -.10014753 4
    1166 510 2002   -.20050375 4
    1166 511 2002   -.10503826 4
    1166 512 2002    -.3212182 4
    1166 513 2002     .4437673 4
    1166 514 2002    .18151404 4
    1166 515 2002   -.16748233 4
    1166 516 2002  -.070448406 4
    1166 517 2002   -.06056389 4
    1166 518 2002   -.07760751 4
    1166 519 2002     .3715606 4
    1166 520 2002    .11765788 4
    1166 521 2002  -.016138405 4
    1166 522 2003    .09858018 4
    1166 523 2003     .0983443 4
    1166 524 2003   -.17749813 4
    1166 525 2003    .16874777 4
    1166 526 2003    .09141434 4
    1166 527 2003    .08301782 4
    1166 528 2003    .20377997 4
    1166 529 2003  -.033443805 4
    1166 530 2003   -.08524045 4
    1166 531 2003   -.05383456 4
    1166 532 2003    .05642015 4
    1166 533 2003   -.05474057 4
    1166 534 2004    -.2002851 4
    1166 535 2004   -.17819238 4
    1166 536 2004  -.015646597 4
    1166 537 2004     .0836684 4
    1166 538 2004    .10904754 4
    1166 539 2004    .03131096 4
    1166 540 2004    .04676875 4
    1166 541 2004    .08513923 4
    1166 542 2004    -.1207189 4
    1166 543 2004    -.1816186 4
    1166 544 2004    .08113027 4
    1166 545 2004    .09968112 5
    1166 546 2005   -.04954542 5
    1166 547 2005 -.0040854593 5
    1166 548 2005  -.074489646 5
    1166 549 2005   -.05107221 5
    1166 550 2005    .08450764 5
    1166 551 2005    .15371233 5
    1166 552 2005    .07936773 5
    1166 553 2005   .025984926 5
    1166 554 2005    .09050346 5
    1166 555 2005  -.031871576 5
    1166 556 2005    -.1236107 5
    1166 557 2005   -.09585842 5
    1166 558 2006    .00260001 5
    1166 559 2006    .12154625 5
    1166 560 2006    .05270199 5
    1166 561 2006  -.003385211 5
    1166 562 2006    .14366731 5
    1166 563 2006   .006545564 5
    1166 564 2006    .08208212 5
    1166 565 2006   .011137736 5
    1166 566 2006  -.037013546 5
    1166 567 2006    .10437811 5
    1166 568 2006     .0767234 5
    1166 569 2006   .018718403 5
    1166 570 2007   .064965375 5
    1166 571 2007  -.035208344 5
    1166 572 2007   .033553373 5
    1166 573 2007  -.007563786 5
    1166 574 2007    -.1611297 5
    1166 575 2007    .04338603 5
    1166 576 2007    -.2311015 5
    1166 577 2007    .03997261 5
    1166 578 2007   -.06573582 5
    1166 579 2007    .27299738 5
    end
    format %tm monthly_date
    Thank you in advance.

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