Dear All, I found this question here (in Chinese). The data set is
Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input long stkcd int year str4 ma float rd
8 2009 "#N/A"        0
8 2010 "#N/A"        0
8 2011 "#N/A"        0
8 2012 "#N/A"        0
8 2013 "#N/A"        0
8 2014 "#N/A"        0
8 2015 "#N/A"        0
8 2016 "YES"   7367428
8 2017 "#N/A" 17148702
8 2018 "#N/A"  7281274
8 2019 "#N/A" 10828121
9 2009 "#N/A"  2930650
9 2010 "#N/A"  3629185
9 2011 "#N/A"  5196702
9 2012 "#N/A"  5190145
9 2013 "#N/A"  3628819
9 2014 "#N/A"  5801677
9 2015 "YES"  10642266
9 2016 "#N/A" 15253602
9 2017 "#N/A" 18787858
9 2018 "#N/A" 24116868
9 2019 "#N/A" 24998574
end
Suppose that there is (at most) one merger and/or acquisition (MA, denoted by the `ma' variable) per `stkcd' across years. MA occurred in the year when "YES" appeared. I'd like to have the following two variables (in the MA year).
  1. I'd like to calculate the mean of `rd' over three years before the MA year.
  2. I'd like to calculate the mean of `rd' over three years after the MA year.