Just to be clear: The statistics below represent the the geographical distribution of the birth places of users of astro.com, i.e. of people with an active interest in astrology.

The figures do not relate to the distribution of general population figures, or state surfaces or anything like that.

It is known that pre-1970 time zone history is represented in TZ database only for the cities which define the zone names.
Other areas of countries are often not correctly represented in TZ database before 1970.

The worst are the USA and Canada, because there, in many states, the authority about daylight time adherence was in the hands of counties or towns, up to the Uniform Timezone Act of 1967.

I am personally responsible for providing correct timezone history for the astrological service company Astrodienst AG in Switzerland, which runs among other things the website www.astro.com

As source for timezone history we use, besides TZ database, the International and American Atlas by Thomas Shanks, and our own research.

The data we have are still far from perfect, because many local details of time zone and daylight saving time use are unknown, especially in the US and Canada.

We have about 25 million birth data records in our database.

I have analyzed to what extent TZ database represents the time zone information correctly, for these data.

I think the results are of some interest for the TZ community.

The overall sums are:

tz_count    24'674'767  data records, 100%
tz_irange   23'675'636 in time range and region which TZ covers correctly, 96%
tz_good        736'769 in time range and region where TZ is unreliable, but correct, 3%
tz_bad         262'362 in time range and region where TZ database gives false result. 1%

This means that only 1% of our astrological charts would be false, if we used TZ database only, without any extra time zone history sources.

More details by country or US/Canada state.
        state        count    in_range %  good %    bad %
USA
     AK (US)         19889         99.6     0.0     0.3         Alaska
     AL (US)         64975         78.6    13.3     8.1         Alabama
     AR (US)         43159         77.2    12.7    10.0         Arkansas
     AZ (US)         96545         97.9     2.0     0.0         Arizona
     CA (US)        981941        100.0     0.0     0.0         California
     CO (US)        107204         99.5     0.5     0.0         Colorado
     CT (US)         89273         95.8     4.2     0.0         Connecticut
     DC (US)         58401         85.7    13.1     1.1         District of Columbia
     DE (US)         14376         91.3     8.5     0.3         Delaware
     FL (US)        241083         89.0     6.5     4.5         Florida
     GA (US)        114613         85.8     7.1     7.2         Georgia (US)
     HI (US)         44070        100.0     0.0     0.0         Hawaii
     IA (US)         50194         72.7    17.1    10.2         Iowa
     ID (US)         23877         92.2     6.4     1.4         Idaho
     IL (US)        267459         90.4     9.5     0.1         Illinois
     IN (US)         88263         76.8    21.6     1.6         Indiana
     KS (US)         45462         74.4    15.0    10.6         Kansas
     KY (US)         56494         74.6    12.5    12.9         Kentucky
     LA (US)         76017         80.3    11.9     7.8         Louisiana
     MA (US)        193439         87.1    12.9     0.1         Massachusetts
     MD (US)         91577         91.2     8.1     0.7         Maryland
     ME (US)         31873         96.8     2.8     0.5         Maine
     MI (US)        185568         86.0    13.3     0.7         Michigan
     MN (US)         95725         75.0    17.0     7.9         Minnesota
     MO (US)         91038         79.4    14.4     6.2         Missouri
     MS (US)         28859         70.0    20.4     9.6         Mississippi
     MT (US)         19767         73.7    24.7     1.5         Montana
     NC (US)        106991         82.9    10.2     6.9         North Carolina
     ND (US)         12427         71.5    17.5    10.9         North Dakota
     NE (US)         28670         69.1    18.2    12.7         Nebraska
     NH (US)         23707         91.2     8.2     0.6         New Hampshire
     NJ (US)        190614         99.6     0.3     0.1         New Jersey
     NM (US)         42651         80.6    18.4     0.9         New Mexico
     NV (US)         36053         99.4     0.4     0.3         Nevada
     NY (US)        628944         96.8     3.0     0.1         New York
     OH (US)        191745         73.9    18.3     7.8         Ohio
     OK (US)         55229         73.7    16.5     9.8         Oklahoma
     OR (US)         98166         87.1     9.8     3.1         Oregon
     PA (US)        228064         89.8     9.7     0.6         Pennsylvania
     PR (US)         37149        100.0     0.0     0.0         Puerto Rico
     RI (US)         26089         97.1     2.8     0.1         Rhode Island
     SC (US)         40233         82.9    10.0     7.1         South Carolina
     SD (US)         12863         72.7    18.6     8.7         South Dakota
     TN (US)         75125         82.9     9.3     7.8         Tennessee
     TX (US)        327328         83.3     9.8     6.9         Texas
     UT (US)         48909         82.7    16.2     1.1         Utah
     VA (US)        109591         85.5    10.1     4.4         Virginia
     VT (US)         17598         86.4    12.7     0.9         Vermont
     WA (US)        159835         84.8    11.9     3.3         Washington
     WI (US)         85917         75.5    18.5     5.9         Wisconsin
     WV (US)         22800         72.7    20.3     7.0         West Virginia
     WY (US)          8962         75.1    23.9     0.9         Wyoming

Canada
    AB (CAN)         64249         97.9     2.0     0.1         Alberta
    BC (CAN)         99214         98.0     2.0     0.0         British Columbia (CAN)
    MB (CAN)         21563         69.8    27.5     2.6         Manitoba (CAN)
    NB (CAN)         10438         89.0     8.3     2.7         New Brunswick (CAN)
    NF (CAN)          7329         98.4     1.2     0.4         Newfoundland (CAN)
    NS (CAN)         18829         75.4    16.3     8.2         Nova Scotia (CAN)
    NT (CAN)          1137         80.7     0.0    19.3         Northwest Territories (CAN)
    ON (CAN)        239755         86.3    12.4     1.3         Ontario (CAN)
    PE (CAN)          2036         80.0    16.1     3.9         Prince Edward Island (CAN)
    QU (CAN)        126300         88.4     9.8     1.8         Quebec (CAN)
    SK (CAN)         24390         78.2    12.4     9.5         Saskatchewan (CAN)
    YK (CAN)           932        100.0     0.0     0.0         Yukon Territories (CAN)

Other countries with significant issues in TZ database, only those with > 1% bad results
          BY         13966         97.1     1.2     1.7         Belarus
         CAR           268         33.2     0.4    66.4         Central African Repub
       CHINA        214617         96.0     2.4     1.6         China
       CONGO          1026         49.9     0.0    50.1         Congo (Brazaville)
       GABON           704         47.7     0.0    52.3         Gabon
        GUAM          3613         45.6     0.0    54.4         Guam
       INDSA         51950         97.2     0.8     2.0         Indonesia
       NIGER           294         76.9     3.7    19.4         Niger
   NIRE (UK)         16228         97.1     0.7     2.1         Northern Ireland
          RU        177880         89.4     8.5     2.1         Russian Federation
       SUDAN          2495          0.0     0.0   100.0         Sudan (?? my be my fault)
        TAAF             2          0.0     0.0   100.0         French Kerguelen Islands
        TANZ          4162         68.3    30.2     1.5         Tanzania
         TOK            17         41.2     0.0    58.8         Tokelau
          UA         71260         95.9     2.4     1.7         Ukraine
        VIET        299630         97.6     0.8     1.6         Vietnam