Hi Statalisters

I want to assess county differences in medication rates in Norway to detect outliers. For this purpose I want to use funnel plots as recommended by Spiegelhalter (see e.g. The Art of Statistics). I am trying this on publically available Norwegian data. However, I have worked on this for some time now and I am not sure whether I am specifying the funnel plot correctly, and I wonder if any of you have some input on this.

Specifically, I am having some trouble with (i) specifying the correct weights (the plot command only works with the -nowei- option), and (ii) the confidence intervals seem to narrow, although I suspect this may be due to sample size, not my specification of the funnel plot.

It's county data for a year so it's a small sample with 18 observations. The medication rate is by 1000 individuals per county. I've gathered population data per county, and made a population rate in 1000's so it's scaled to the medication rate.

I obtain the standard deviation of the medication rate by
Code:
egen sd_medrate=sd(medrate1000)
The funnel plot command is then:
Code:
funnelcompar medrate1000 poprate1000 county sd_medrate, cont nowei
Which gives:
Array

Without -nowei- I get the following error message:
Code:
may not use noninteger frequency weights
As it's such a small sample, I'll include the total dataset in dataex:
Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input long county float(county_pop medrate1000 poprate1000 sd_medrate)
 4  72856 6.37  72.856 1.6318192
12 107080 4.68  107.08 1.6318192
 2 108499 9.68 108.499 1.6318192
14 156494 4.76 156.494 1.6318192
13 168231 7.46 168.231 1.6318192
16 170377  6.4 170.377 1.6318192
 9 185216 5.56 185.216 1.6318192
 5 190709 8.24 190.709 1.6318192
17 231286 7.83 231.286 1.6318192
 8 236271 9.19 236.271 1.6318192
 7 251262 5.87 251.262 1.6318192
 3 257673 6.28 257.673 1.6318192
18 271662 7.59 271.662 1.6318192
15 422102 5.61 422.102 1.6318192
11 427947 6.51 427.947 1.6318192
 6 477175 4.79 477.175 1.6318192
 1 536499 5.32 536.499 1.6318192
10 586860 3.62  586.86 1.6318192
end
label values county fylke
label def fylke 1 "Akershus", modify
label def fylke 2 "Aust-Agder", modify
label def fylke 3 "Buskerud", modify
label def fylke 4 "Finnmark", modify
label def fylke 5 "Hedmark", modify
label def fylke 6 "Hordaland", modify
label def fylke 7 "Møre og Romsdal", modify
label def fylke 8 "Nordland", modify
label def fylke 9 "Oppland", modify
label def fylke 10 "Oslo", modify
label def fylke 11 "Rogaland", modify
label def fylke 12 "Sogn og Fjordane", modify
label def fylke 13 "Telemark", modify
label def fylke 14 "Troms", modify
label def fylke 15 "Trøndelag", modify
label def fylke 16 "Vest-Agder", modify
label def fylke 17 "Vestfold", modify
label def fylke 18 "Østfold", modify