Population Change 2020-2021

This notebook demonstrates how to query and merge the same data set from different years. It also demonstrates how, behind the scenes, censusdis loads metadata and works across multiple years. Nothing is hard-coded in the library about what variables or data sets are available in what years. So when the 2021 data was published, this notebook just worked.

[1]:

# So we can run from within the censusdis project and find the packages we need.
import os
import sys

sys.path.append(
    os.path.join(os.path.abspath(os.path.join(os.path.curdir, os.path.pardir)))
)

Imports and configuration

[2]:

import censusdis.data as ced
import censusdis.maps as cem

[3]:

DATASET = "acs/acs5"

[4]:

TOTAL_POPULATION_VARIABLE = "B01003_001E"

Download the popluation of the states in both years

[5]:

gdf_states_2020 = ced.download_detail(
    DATASET, 2020, ["NAME", TOTAL_POPULATION_VARIABLE], state="*", with_geometry=True
)

# Note that we don't load the geometry here.
# We already have it above, and it will
# still be available after the merge.
df_states_2021 = ced.download_detail(
    DATASET, 2021, ["NAME", TOTAL_POPULATION_VARIABLE], state="*"
)

Merge the two data sets and compute how the populations changed

[6]:

gdf_both_years = gdf_states_2020.merge(
    df_states_2021, on=["STATE", "NAME"], suffixes=("_2020", "_2021")
)

[7]:

TOTAL_POPULATION_2020_VARIABLE = f"{TOTAL_POPULATION_VARIABLE}_2020"
TOTAL_POPULATION_2021_VARIABLE = f"{TOTAL_POPULATION_VARIABLE}_2021"

TOTAL_POPULATION_CHANGE = f"{TOTAL_POPULATION_VARIABLE}_DELTA"
TOTAL_POPULATION_CHANGE_PERCENT = f"{TOTAL_POPULATION_CHANGE}_PERCENT"

[8]:

gdf_both_years[TOTAL_POPULATION_CHANGE] = (
    gdf_both_years[TOTAL_POPULATION_2021_VARIABLE]
    - gdf_both_years[TOTAL_POPULATION_2020_VARIABLE]
)

gdf_both_years[TOTAL_POPULATION_CHANGE_PERCENT] = (
    100
    * gdf_both_years[TOTAL_POPULATION_CHANGE]
    / gdf_both_years[TOTAL_POPULATION_2020_VARIABLE]
)

Fastest growing states

Absolute

[9]:

gdf_both_years.sort_values(TOTAL_POPULATION_CHANGE, ascending=False)[
    ["NAME", TOTAL_POPULATION_CHANGE]
].head()

[9]:

	NAME	B01003_001E_DELTA
4	New York	599896
29	New Jersey	348606
24	Texas	227139
0	Pennsylvania	175765
7	Florida	122838

Percentagewise

[10]:

gdf_both_years.sort_values(TOTAL_POPULATION_CHANGE_PERCENT, ascending=False)[
    ["NAME", TOTAL_POPULATION_CHANGE_PERCENT]
].head()

[10]:

	NAME	B01003_001E_DELTA_PERCENT
29	New Jersey	3.923349
19	Idaho	3.263285
42	Rhode Island	3.228499
4	New York	3.074049
32	Vermont	2.770446

Fastest shrinking states

Absolute

[11]:

gdf_both_years.sort_values(TOTAL_POPULATION_CHANGE, ascending=True)[
    ["NAME", TOTAL_POPULATION_CHANGE]
].head()

[11]:

	NAME	B01003_001E_DELTA
16	Arizona	-94861
33	North Carolina	-19205
5	District of Columbia	-18820
39	Mississippi	-14812
8	South Carolina	-12614

Percentagewise

[12]:

gdf_both_years.sort_values(TOTAL_POPULATION_CHANGE_PERCENT, ascending=True)[
    ["NAME", TOTAL_POPULATION_CHANGE_PERCENT]
].head()

[12]:

	NAME	B01003_001E_DELTA_PERCENT
5	District of Columbia	-2.681011
16	Arizona	-1.322277
15	Wyoming	-0.809670
39	Mississippi	-0.496741
2	West Virginia	-0.352822

Plot on maps

[13]:

from matplotlib.ticker import FuncFormatter

ax = cem.plot_us(
    gdf_both_years,
    TOTAL_POPULATION_CHANGE,
    legend=True,
    figsize=(12, 6),
    cmap="PRGn",
    edgecolor="black",
    linewidth=0.25,
    vmin=-600_000,
    vmax=600_000,
    legend_kwds={"format": FuncFormatter(lambda x, pos: f"{x:+,.0f}")},
)

ax.axis("off")
ax.set_title("Total Population Change by State, 2020-2021")

[13]:

Text(0.5, 1.0, 'Total Population Change by State, 2020-2021')

../_images/nb_Population_Change_2020-2021_24_1.png

[14]:

ax = cem.plot_us(
    gdf_both_years,
    TOTAL_POPULATION_CHANGE_PERCENT,
    legend=True,
    figsize=(12, 6),
    cmap="PRGn",
    edgecolor="black",
    linewidth=0.25,
    vmin=-4,
    vmax=4,
    legend_kwds={"format": FuncFormatter(lambda x, pos: f"{x:+.1f}%")},
)

ax.axis("off")
ax.set_title("Total Population Percentage Change by State, 2020-2021")

[14]:

Text(0.5, 1.0, 'Total Population Percentage Change by State, 2020-2021')

../_images/nb_Population_Change_2020-2021_25_1.png

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