12 Aug
2019
12 Aug
'19
9:58 a.m.
To All
We are working to collect information about the resident labor force in Cambridge,
Massachusetts. We set the residence as the State-Place of Cambridge city, MA, and the
workplace as POW State-Place of Cambridge city, MA.
The numbers in the CTPP Flows tables are not adding up as expected. Table A304100 - Total
workers (1) (Workers 16 years and over) provides an estimate of 27,725 (MOE 847), whereas
Table B303100 - Household income in the past 12 months (2016$) (9) (Workers 16 years and
over in households) provides a total estimate of 37,300 (MOE 2,054). Furthermore, when we
add up the count of workers in each income bracket in Table B303100 they sum to 22,470.
I could understand if the total number of resident workers 16 and older in households was
smaller than total workers over 16, but we cannot make sense of how the reverse could be
true. It also doesn't explain why the sum of all categories is smaller than the
listed total. Could data suppression account for this? That would seem unlikely at the
level of a city of our size. Could the results be due to data suppression at smaller
geographic levels having a ripple effect on a larger geo? I understand workers with an
unclear or imprecise work address are excluded from the flow data. Are these issues a
result of that screening or is this a different type of issue?
Interestingly, the numbers make sense as expected when we look at the Residence tables for
the same geography. Table A102101 - Total workers (1) (Workers 16 years and over) provides
an estimate of 61,925 (MOE 1,008) and Table A103100 - Total Workers in households (1)
(Workers 16 years and over in households) estimates 54,195 (MOE 1,075).
Any help on interpreting our resident labor force stats is appreciated.
Cliff Cook
Clifford Cook
Senior Planning Information Manager
Cambridge Community Development Department
344 Broadway, Cambridge, MA. 02139
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12 Aug
12 Aug
11:56 a.m.
Cliff--let me take a shot at this. Between the ACS and CTPP concepts
there are a lot subtleties and a lot going on.
1. First you are working with Part 3 or Flow tables. Some of which have
perturbation applied to them and some that do not. Perturbation is what
allows the CTPP to meet all the DRB requirements. Although perturbed and
non perturbed tables are mutually exclusive so you will never have the
same table, one with disclosure and one with out. However, that does not
explain your difference. I only point it out to give that broader
understanding of the data structure. If you look at the first letter of
the table number "A" in not pertabated and "B" is not. The first two
Part 3-flow tables total workers and workers by mode are not pertabated
and show 27,725 people living and working in Cambridge. If you look at
tables B302101 (age) and 302012 (industry) they show 27,735 people
living and working in Cambridge. The difference of 10 I submit is the
effect of perturbation.
2. In the other tables you reference, except for income I am thinking
the drop in the total is the difference between ALL workers including
those in group quarters and just workers in households. With CTPP tables
since many of the tables were developed for travel modeling their
universes are restricted to just workers in households. Right now I do
not have an explanation for the increase in workers you saw with the
income table without talking to some people and digging into it more.
Since I worked with all the previous vintages of CTPP tables and the
Bureaus rules have changed I do not want to speculate. It was
encouraging that the B303100 and B303201 were in agreement.
Lets keep the discussion going and hopefully we can get to the bottom of
this. Usually it is something simple but you never know. thanks for
airing this.
On 8/12/2019 9:58 AM, Cook, Cliff wrote:
To All
We are working to collect information about the resident labor force
in Cambridge, Massachusetts. We set the residence as the State-Place
of Cambridge city, MA, and the workplace as POW State-Place of
Cambridge city, MA.
The numbers in the CTPP Flows tables are not adding up as expected.
Table A304100 – Total workers (1) (Workers 16 years and over) provides
an estimate of _27,725_ (MOE 847), whereas Table B303100 – Household
income in the past 12 months (2016$) (9) (Workers 16 years and over in
households) provides a total estimate of _37,300_ (MOE 2,054).
Furthermore, when we add up the count of workers in each income
bracket in Table B303100 they sum to _22,470_.
I could understand if the total number of resident workers 16 and
older in households was smaller than total workers over 16, but we
cannot make sense of how the reverse could be true. It also doesn’t
explain why the sum of all categories is smaller than the listed
total. Could data suppression account for this? That would seem
unlikely at the level of a city of our size. Could the results be due
to data suppression at smaller geographic levels having a ripple
effect on a larger geo? I understand workers with an unclear or
imprecise work address are excluded from the flow data. Are these
issues a result of that screening or is this a different type of issue?
Interestingly, the numbers make sense as expected when we look at the
Residence tables for the same geography. Table A102101 – Total workers
(1) (Workers 16 years and over) provides an estimate of 61,925 (MOE
1,008) and Table A103100 – Total Workers in households (1) (Workers 16
years and over in households) estimates 54,195 (MOE 1,075).
Any help on interpreting our resident labor force stats is appreciated.
Cliff Cook
*Clifford Cook
Senior Planning Information Manager*
Cambridge Community Development Department
344 Broadway, Cambridge, MA. 02139
cid:image001.png@01CF4355.A65408C0<https://www.facebook.com/CDDat344>cid:image002.jpg@01CF4357.3478C720<https://twitter.com/cddat344>cid:image010.jpg@01CF4357.3478C720<http://instagram.com/cddat344>
*www.cambridgema.gov/CDD*<http://www.cambridgema.gov/CDD.aspx>**
ccook@cambridgema.gov<mailto:ccook@cambridgema.gov>
M: 8:30-8:00 T-Th: 8:30-5:00 F: 8:30-Noon
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--
Ed Christopher
Transportation Planning Consultant
708-269-5237
12:10 p.m.
Ed
Thanks for the information. I am unsure about one you thing you wrote "If you look
at the first letter of the table number "A" in not perturbated and "B"
is not" Did you mean to say that tables ending in B ARE perturbated?
Thanks
Cliff
From: Ed Christopher <edc(a)berwyned.com>
Sent: Monday, August 12, 2019 12:57 PM
To: ctpp-news(a)chrispy.net; Cook, Cliff <ccook(a)cambridgema.gov>
Cc: Werner, Bailey <bwerner(a)cambridgema.gov>
Subject: Re: [CTPP] 2012-16 CTPP Question about Counts
Cliff--let me take a shot at this. Between the ACS and CTPP concepts there are a lot
subtleties and a lot going on.
1. First you are working with Part 3 or Flow tables. Some of which have perturbation
applied to them and some that do not. Perturbation is what allows the CTPP to meet all the
DRB requirements. Although perturbed and non perturbed tables are mutually exclusive so
you will never have the same table, one with disclosure and one with out. However, that
does not explain your difference. I only point it out to give that broader understanding
of the data structure. If you look at the first letter of the table number "A"
in not pertabated and "B" is not. The first two Part 3-flow tables total workers
and workers by mode are not pertabated and show 27,725 people living and working in
Cambridge. If you look at tables B302101 (age) and 302012 (industry) they show 27,735
people living and working in Cambridge. The difference of 10 I submit is the effect of
perturbation.
2. In the other tables you reference, except for income I am thinking the drop in the
total is the difference between ALL workers including those in group quarters and just
workers in households. With CTPP tables since many of the tables were developed for travel
modeling their universes are restricted to just workers in households. Right now I do
not have an explanation for the increase in workers you saw with the income table without
talking to some people and digging into it more. Since I worked with all the previous
vintages of CTPP tables and the Bureaus rules have changed I do not want to speculate. It
was encouraging that the B303100 and B303201 were in agreement.
Lets keep the discussion going and hopefully we can get to the bottom of this. Usually it
is something simple but you never know. thanks for airing this.
On 8/12/2019 9:58 AM, Cook, Cliff wrote:
To All
We are working to collect information about the resident labor force in Cambridge,
Massachusetts. We set the residence as the State-Place of Cambridge city, MA, and the
workplace as POW State-Place of Cambridge city, MA.
The numbers in the CTPP Flows tables are not adding up as expected. Table A304100 - Total
workers (1) (Workers 16 years and over) provides an estimate of 27,725 (MOE 847), whereas
Table B303100 - Household income in the past 12 months (2016$) (9) (Workers 16 years and
over in households) provides a total estimate of 37,300 (MOE 2,054). Furthermore, when we
add up the count of workers in each income bracket in Table B303100 they sum to 22,470.
I could understand if the total number of resident workers 16 and older in households was
smaller than total workers over 16, but we cannot make sense of how the reverse could be
true. It also doesn't explain why the sum of all categories is smaller than the
listed total. Could data suppression account for this? That would seem unlikely at the
level of a city of our size. Could the results be due to data suppression at smaller
geographic levels having a ripple effect on a larger geo? I understand workers with an
unclear or imprecise work address are excluded from the flow data. Are these issues a
result of that screening or is this a different type of issue?
Interestingly, the numbers make sense as expected when we look at the Residence tables for
the same geography. Table A102101 - Total workers (1) (Workers 16 years and over) provides
an estimate of 61,925 (MOE 1,008) and Table A103100 - Total Workers in households (1)
(Workers 16 years and over in households) estimates 54,195 (MOE 1,075).
Any help on interpreting our resident labor force stats is appreciated.
Cliff Cook
Clifford Cook
Senior Planning Information Manager
Cambridge Community Development Department
344 Broadway, Cambridge, MA. 02139
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--
Ed Christopher
Transportation Planning Consultant
708-269-5237
12:35 p.m.
Tables Starting with B are perturbated. Tables starting with an A are
not. Here is the generalized coding schema for the tables.
"The tables are divided into three parts. Part 1 summarizes the
population at their place of residence; Part 2 the workers at their
place of work and Part 3 the commuting flow from home to work. Each
table has a unique number. The number is partially encoded. Reading from
left to right, all tables will begin with a letter, either an ‘A’ or a
‘B’. The ‘A’ means the table is derived directly from standard ACS data
while ‘B’ tables have put through a special privacy protection
algorithm. The next digit identifies which part the data belongs to--a
‘1’ for part one, ‘2’ for part two and ‘3’ for part three. The next two
digits refer to the universe from which the data is drawn. There are 16
different universes and they are listed later on page 13 of this guide.
The next digit lets the user know if the table is a univariate (1),
two-way (2) or three-way (3) table. The next 2 digits represent a
sequential numbering of the tables."
You can read all about the peturbation here:
https://www.nap.edu/download/18160
On 8/12/2019 12:10 PM, Cook, Cliff wrote:
Ed
Thanks for the information. I am unsure about one you thing you wrote
“If you look at the first letter of the table number "A" in not
perturbated and "B" is not” Did you mean to say that tables ending in
B ARE perturbated?
Thanks
Cliff
*From:*Ed Christopher <edc(a)berwyned.com>
*Sent:* Monday, August 12, 2019 12:57 PM
*To:* ctpp-news(a)chrispy.net; Cook, Cliff <ccook(a)cambridgema.gov>
*Cc:* Werner, Bailey <bwerner(a)cambridgema.gov>
*Subject:* Re: [CTPP] 2012-16 CTPP Question about Counts
Cliff--let me take a shot at this. Between the ACS and CTPP concepts
there are a lot subtleties and a lot going on.
1. First you are working with Part 3 or Flow tables. Some of which
have perturbation applied to them and some that do not. Perturbation
is what allows the CTPP to meet all the DRB requirements. Although
perturbed and non perturbed tables are mutually exclusive so you will
never have the same table, one with disclosure and one with out.
However, that does not explain your difference. I only point it out to
give that broader understanding of the data structure. If you look at
the first letter of the table number "A" in not pertabated and "B" is
not. The first two Part 3-flow tables total workers and workers by
mode are not pertabated and show 27,725 people living and working in
Cambridge. If you look at tables B302101 (age) and 302012 (industry)
they show 27,735 people living and working in Cambridge. The
difference of 10 I submit is the effect of perturbation.
2. In the other tables you reference, except for income I am thinking
the drop in the total is the difference between ALL workers including
those in group quarters and just workers in households. With CTPP
tables since many of the tables were developed for travel modeling
their universes are restricted to just workers in households. Right
now I do not have an explanation for the increase in workers you saw
with the income table without talking to some people and digging into
it more. Since I worked with all the previous vintages of CTPP tables
and the Bureaus rules have changed I do not want to speculate. It was
encouraging that the B303100 and B303201 were in agreement.
Lets keep the discussion going and hopefully we can get to the bottom
of this. Usually it is something simple but you never know. thanks for
airing this.
On 8/12/2019 9:58 AM, Cook, Cliff wrote:
To All
We are working to collect information about the resident labor
force in Cambridge, Massachusetts. We set the residence as the
State-Place of Cambridge city, MA, and the workplace as POW
State-Place of Cambridge city, MA.
The numbers in the CTPP Flows tables are not adding up as
expected. Table A304100 – Total workers (1) (Workers 16 years and
over) provides an estimate of _27,725_ (MOE 847), whereas Table
B303100 – Household income in the past 12 months (2016$) (9)
(Workers 16 years and over in households) provides a total
estimate of _37,300_ (MOE 2,054). Furthermore, when we add up the
count of workers in each income bracket in Table B303100 they sum
to _22,470_.
I could understand if the total number of resident workers 16 and
older in households was smaller than total workers over 16, but we
cannot make sense of how the reverse could be true. It also
doesn’t explain why the sum of all categories is smaller than the
listed total. Could data suppression account for this? That
would seem unlikely at the level of a city of our size. Could the
results be due to data suppression at smaller geographic levels
having a ripple effect on a larger geo? I understand workers with
an unclear or imprecise work address are excluded from the flow
data. Are these issues a result of that screening or is this a
different type of issue?
Interestingly, the numbers make sense as expected when we look at
the Residence tables for the same geography. Table A102101 – Total
workers (1) (Workers 16 years and over) provides an estimate of
61,925 (MOE 1,008) and Table A103100 – Total Workers in households
(1) (Workers 16 years and over in households) estimates 54,195
(MOE 1,075).
Any help on interpreting our resident labor force stats is
appreciated.
Cliff Cook
*Clifford Cook
Senior Planning Information Manager*
Cambridge Community Development Department
344 Broadway, Cambridge, MA. 02139
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--
Ed Christopher
Transportation Planning Consultant
708-269-5237
--
Ed Christopher
Transportation Planning Consultant
708-269-5237
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