| An important object to keep in mind about ZIP code | | | | dramatic downward trend in the population of 63301 |
| finder is that they change over time. In some cases | | | | since 1980, when in fact just the opposite is true. |
| these change can be quite amazing, but more | | | | What the world really needs to deal with ZIP code |
| frequently they are small and subtle. When a ZIP code | | | | natural features properly is a large geographic |
| changes its definition it does not change its name like a | | | | equivalence organizer linking ZIP code finder to other |
| census zone. The ZIP code that was called '63301' in | | | | relevant geographies with a time aspect. Instead, what |
| St. Charles County, Mo in 1985 has since been broken | | | | we have is such an equivalence file that relates ZIP |
| into first two and now three ZIP codes. These new | | | | codes to geographic entities primarily used for taking |
| codes were not called 63301.01, 63301.02 and 63301.03; | | | | the 1990 census. This file uses ZIP codes as they |
| they were called 63301, 63303 and 63304. So what is | | | | were defined around July of 1991. What we are |
| referred to as 63301 today represent about a third of | | | | referring to here is the ZIP CODE FINDER |
| the area that it referred to in 1985. The new code | | | | DATABASE and the corresponding Braintech web |
| 63303 did not exist 12 years ago and it has already | | | | application for programming script which we'll be |
| changed its definition so that it now represents about | | | | discussion about in more detail is visit you site. For now, |
| partially of the area it included when it was to begin | | | | what we want to emphasize is that when we talk |
| with created. What this means, of course, is that ZIP | | | | about ZIP codes we really need to keep a time |
| codes are really terrible units for doing any kind of | | | | reference in mind. Just as when you work with census |
| time-series analysis unless you have some way of | | | | tracts you need to know whether you mean 1980 or |
| keeping track of all the changes over time. Otherwise, | | | | 1990 tracts, or when you are talking about the |
| you may wind up concluding that there has been a | | | | countries of Europe -- time is an important dimension. |