Is Portland Getting Taken Over?

Background

I hear talk all the time about Portland’s population growing bigger and bigger, and of people coming from out of state.  I have heard heated debates about how Californian’s are taking over the city because cities such as Los Angelos and San Fransisco are becoming unaffordable.  Gossip tells of property values increasing because of an influx of outsiders.

I myself, have noticed that I tend to meet more people who came from out of state then who are Oregon born, and that those from Oregon are not originally from outside of Multnomah County.  It makes sense that people from Lewis and Clark College would come from outside of Portland, as it is often the case with liberal arts colleges that students move to a new city for school.  But this has also been the case with people I meet outside of the Lewis and Clark circle.

My experience with socializing does not count as facts, however, about the larger demographic information within Portland and Multnomah County.  Nor do rumors count as facts.  This has inspired me to ask and research if Portland is actually growing significantly due to out of state migration.

Methods

To investigate this question, I created three maps comparing 2010 and 2017.  For my demographic data, I used American Fact Finder to download demographic data based on Census tracks from the American Community Survey (ACS). Their most recent usable data is from 2017, and I determined this was usable as my recent data, because 2019 has just begun so 2017 data is probably pretty close to what perfectly up to date data would look like.  I chose 2010 as my earlier comparison year, because it is recent enough to still have reliable data and evaluate is population growth has been as rapid as people say, but far enough in the past to reasonably expect a growth pattern.  I joined data I found from American Fact Finder with shape-file census tract data of Multnomah county from Tigerline.com.  I also used a shape file I downloaded from Tigerline of the City Boundary lines of Portland.  After joining cleaned up demographic data to the shape file layers by the Census tract field, I used quantifying, graduated symbology to show patterns in the information I wanted to highlight.

My first two maps (Fig. 1) show Multnomah County’s population per square mile in 2010 and 2017.  My second two maps (fig. 2) compare the populations per square mile in Multnomah County from out of state in 2010 versus 2017.  My final maps (Fig. 3) show Multnomah County’s in state population per square mile during these two years.  To normalize the data for all of the maps to show population density, I had to create a new field in the attribute table calculating area per square mile, which I created using the geographic calculator in ArcGIS.

Results/Discussion

Looking at figure 1, there is little, but still noticeable difference in population density between 2010 and 2017.  In 2010, none of the census tracks appear to go above a population density of 8000-1200 people per square mile.  In 2017, the number of Census tracks with populations per square mile between 8000 and 12000 increase, and population densities between 12000 and 20000 people per square mile appear.  The only changes in the area outside of Portland is 2 Census Tracks whose populations increase.

Fig. 1

Portland2.jpg

Fig. 2 shows that the population density of people born out of state does not change substantially.  Outside of Portland, the amount of people in Portland per square mile born outside of Oregon stays under 3000 both in 2010 and 2017.  Within the city, there is some increase in people born from another state, particularly you see a change in southwest Portland.  There are a few more tracks within Portland in 2017 in which the population of outsiders increases to over 9,000.  Please note that Fig. 1 and 2 can not be compared by color, as they are categorized due to different numbers of people needing to be represented.

Fig. 2

Portland3.jpg

Results indicate there are more people from out of state then in state in Portland in 2010, and even more so in 2017.  In no census tract does the population density for Fig. 3, showing in state population exceed 6,000.  This goes for both 2010 and 2017.  Furthermore, Fig. 3 shows less change between 2010 and 2017 than Figs 1 and 2, meaning the population of Multnomah county born in-state is relatively stable, while the total population and population born out of state is increasing.  Comparing this informationshows that population in Portland does appear to be increasing in population to some degree due at least in part to people moving into Multnomah County from other states.  What is interesting, is that the suburbs appear to have a larger in state population than out of state population.  In some tracts in Fig. 3, the population reaches between 3000 and 6000, while in Fig 2. the population of residents born out of state does not reach above 3,000 at any given point.  This suggests residents born out of state are predominantly moving within the city limits.

Fig. 3

Portland4.jpg

These maps have limitations, as the number of people in are categorized into groupings.  One census tract may remain 1 color in any of these maps because the population represented only increases or decreases by 1,000, while the maps group the changes together by either 3,000 or 4,000.  I choose to only use 5 categories to show the data, however, for legibility.  With more categories, the colors would be very similar and difficult to discern from one another.

While these maps only show very small changes in population density between 2010 and 2017 for the total, in state and out of state, that does not mean there has not been significant changes that these maps can not represent. Raw numbers would show more minute changes in total, in-state, and out of state population densities. ___  Showing data that goes further back would also show a greater comparison and allow more changes to be observed.  Furthermore, data on the percent of the population that is from California would get to the heart of the rumor that Portland’s population increase it due primarily from Californians moving in.

These maps do still convey any drastic changes in specific census tracks, and prevent exaggeration of the facts.  It is easy to claim that Portland is “being taken over” or “a completely different city,” but these maps show that while change may be occurring, it is not as drastic or rapid as people might make it seem.

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