I'm studying the causal effects of a state policy, nurse practitioner scope of practice law, on various outcomes (3 different studies). States' policies are categorized as restricted, reduced, and full practice. I've simplified to look at just restricted states and states that change policy from restricted to reduced as I'm learning to apply this method for my dissertation. Policy changes at different times for multiple states during the study period (2010-2017). I'm trying to verify whether my data setup is solid.

In this example, my outcome is totnp (count of nurse practitioners). The unit of observation is county/year. The scope of practice policy changes occur at the state level. Independent variables are year (2010-2017), totclinics (total clinics), totpop (total population), unemployment (rate), and fips (group variable state/county fips). time0_rest_red is the time indicator variable where 0 = not treated, 1 = treatment year and beyond.

Given this outcome is a count variable I've elected to use poisson and use xtset to establish a panel dataset. The treatment group is made up from counties in states that change state scope of practice law from restricted to reduced. The control group is made up from counties in states that have restricted scope of practice laws during the entire study period (2010-2017). I have a second potential control group, counties in states that have full practice scope of practice laws during the entire study period; I don't find examples of how to set this up.

xtset fips year
xtpoisson totnp time0_rest_red i.fips i.year if study1a_sample==1, fe vce(robust)

Thanks in advance for weighing in. My sample code is below.

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input int totnp float time0_rest_red int(year totclinics) long totpop float unemployment long fips float study1a_sample
 18 0 2010  7  82291 11.6 61 1
  2 0 2010  2  13228 16.3 18 1
 29 0 2010  3 119490  9.6 52 1
  0 0 2010  1  11539 12.8 19 1
  2 0 2010  3  23068 17.2 50 1
 22 0 2010  4  67023 10.7 64 1
  8 0 2010  1  21027 12.3 46 1
  2 0 2010  0  17302  9.4 34 1
  2 0 2010  1  14972  8.3 15 1
 18 0 2010  2  41616 12.9 62 1
  7 0 2010  1  83593  9.1 58 1
  5 0 2010  1  43820 17.4 24 1
  6 0 2010  3  34339   11 40 1
  0 0 2010  2   9045 17.3 32 1
 22 0 2010  1  82782  8.2 42 1
341 0 2010  8 658466  9.4 37 1
 33 0 2010  2  80406  8.7 22 1
 52 0 2010  0 101547  8.4 35 1
 24 0 2010  1 195085  6.9 59 1
  4 0 2010  3  20947 12.3  7 1
139 0 2010  3 334811  7.4 45 1
  2 0 2010  2  52947 10.3 57 1
 18 0 2010  1  21452 12.8 44 1
 31 0 2010  3 182265  8.9  2 1
103 0 2010  4 229363  9.2 51 1
  2 0 2010  4  27457 11.7  3 1
 12 0 2010  1  32899  8.2 55 1
  2 0 2010  1  34215 13.7  9 1
 39 0 2010  3  92709  8.8 39 1
  4 0 2010  3  13763 14.5 60 1
 31 0 2010  2 118572  9.7  8 1
 16 0 2010  3  37765  9.1 20 1
  3 0 2010  1  26790  8.9 31 1
 12 0 2010  6  22913 12.6 56 1
  6 0 2010  2  13906  8.7 21 1
 18 0 2010  5  71109 11.6 25 1
  2 0 2010  4  11670 21.3 66 1
  4 0 2010  2  13859 11.3 12 1
 13 0 2010  1  50251  8.5 23 1
  3 0 2010  0  13932 13.8 14 1
  6 0 2010  5  25833 15.6 13 1
  0 0 2010  0  43643  9.2 11 1
 10 0 2010  1  79303  8.5 26 1
 14 0 2010 10  53227  9.7 36 1
  8 0 2010  1  30776 13.3 47 1
 32 0 2010  1  54428  9.8 17 1
  2 0 2010  2  19746 11.4 54 1
  3 0 2010  8  38319 11.1 27 1
  1 0 2010  1  25989  9.3 10 1
  2 0 2010  2  11299 16.3 43 1
  7 0 2010  4  31704 10.2 30 1
  2 0 2010  2  14564 12.9 38 1
  3 0 2010  1  54571  7.8  1 1
 28 0 2010  0 140247  8.1 41 1
  3 0 2010  2  17581 13.3 65 1
 33 0 2010  9 104430  9.5 28 1
135 0 2010 15 412992 10.2 49 1
  7 0 2010  0  49948  7.4 16 1
 13 0 2010  6  93019  8.6 48 1
  4 0 2010  2  15760 13.4 33 1
  7 0 2010  3  22915 10.3  4 1
 86 0 2010  3 194656  8.5 63 1
  2 0 2010  3  10591 16.1 53 1
  4 0 2010  0  17241 11.7 29 1
  6 0 2010  3  24484 15.1 67 1
  3 0 2010  2  10914 14.7  6 1
  3 0 2010  3  57322    9  5 1
 16 0 2011 10  53291  8.7 36 1
 37 0 2011  1  54512    9 17 1
  8 0 2011  0  50526  7.1 16 1
  5 0 2011  8  38095 10.5 27 1
  5 0 2011  2  55267    8  1 1
  3 0 2011  4  11482 19.3 66 1
  2 0 2011  1  14835  8.3 15 1
  3 0 2011  2  17344   14 65 1
  2 0 2011  3  11147 16.6 43 1
  4 0 2011  3  10542 15.3  6 1
  7 0 2011  3  22766  9.9  4 1
  2 0 2011  1  17412  8.4 34 1
 32 0 2011  2 119953  8.7 52 1
 10 0 2011  2  80162  8.3 26 1
 39 0 2011 10 104303  9.1 28 1
 12 0 2011  1  84398  8.3 58 1
 35 0 2011  2  80536  8.1 22 1
 13 0 2011  1  32915  7.8 55 1
  5 0 2011  0  17182 10.4 29 1
  6 0 2011  2  13911  8.7 21 1
  2 0 2011  3  13478 14.5 60 1
  6 0 2011  2  43332 16.2 24 1
  2 0 2011  2  19349 10.7 54 1
126 0 2011  5 232032  9.1 51 1
 99 0 2011  3 197211  8.2 63 1
  3 0 2011  4  27119 11.4  3 1
390 0 2011  8 658931  8.7 37 1
 27 0 2011  4  66661  9.5 64 1
  3 0 2011  3  22760 15.3 50 1
  5 0 2011  5  25695 15.2 13 1
 12 0 2011  1  50044  8.3 23 1
 56 0 2011  0 102369  8.1 35 1
  4 0 2011  0  13862 11.8 14 1
end
label values fips fips
label def fips 1 "1 1", modify
label def fips 2 "1 3", modify
label def fips 3 "1 5", modify
label def fips 4 "1 7", modify
label def fips 5 "1 9", modify
label def fips 6 "1 11", modify
label def fips 7 "1 13", modify
label def fips 8 "1 15", modify
label def fips 9 "1 17", modify
label def fips 10 "1 19", modify
label def fips 11 "1 21", modify
label def fips 12 "1 23", modify
label def fips 13 "1 25", modify
label def fips 14 "1 27", modify
label def fips 15 "1 29", modify
label def fips 16 "1 31", modify
label def fips 17 "1 33", modify
label def fips 18 "1 35", modify
label def fips 19 "1 37", modify
label def fips 20 "1 39", modify
label def fips 21 "1 41", modify
label def fips 22 "1 43", modify
label def fips 23 "1 45", modify
label def fips 24 "1 47", modify
label def fips 25 "1 49", modify
label def fips 26 "1 51", modify
label def fips 27 "1 53", modify
label def fips 28 "1 55", modify
label def fips 29 "1 57", modify
label def fips 30 "1 59", modify
label def fips 31 "1 61", modify
label def fips 32 "1 63", modify
label def fips 33 "1 65", modify
label def fips 34 "1 67", modify
label def fips 35 "1 69", modify
label def fips 36 "1 71", modify
label def fips 37 "1 73", modify
label def fips 38 "1 75", modify
label def fips 39 "1 77", modify
label def fips 40 "1 79", modify
label def fips 41 "1 81", modify
label def fips 42 "1 83", modify
label def fips 43 "1 85", modify
label def fips 44 "1 87", modify
label def fips 45 "1 89", modify
label def fips 46 "1 91", modify
label def fips 47 "1 93", modify
label def fips 48 "1 95", modify
label def fips 49 "1 97", modify
label def fips 50 "1 99", modify
label def fips 51 "1 101", modify
label def fips 52 "1 103", modify
label def fips 53 "1 105", modify
label def fips 54 "1 107", modify
label def fips 55 "1 109", modify
label def fips 56 "1 111", modify
label def fips 57 "1 113", modify
label def fips 58 "1 115", modify
label def fips 59 "1 117", modify
label def fips 60 "1 119", modify
label def fips 61 "1 121", modify
label def fips 62 "1 123", modify
label def fips 63 "1 125", modify
label def fips 64 "1 127", modify
label def fips 65 "1 129", modify
label def fips 66 "1 131", modify
label def fips 67 "1 133", modify