On the menu this week are the salaries of Baltimore City employees for the 2015 fiscal year, a popular data set available at Open Baltimore. These data include both annual salaries and gross pay, and we’ll start off this post with the top ten for each category. Not too surprising, those who hold senior positions in the city’s government receive the highest annuals salaries:

Name Title (Agency) Annual Salary
Marilyn Mosby State’s Attorney (State’s Attorney’s Office) $238,772
Anthony Batts Commissioner (Police) $211,785
Leana Wen Executive Director III (Health) $200,000
Henry Raymond Executive Director III (Finance) $192,500
Kaliope Parthemos Executive Director V (Mayor’s Office) $178,900
William Johnson Executive Director III (Transportation) $176,015
Niles Ford Executive Director III (Fire) $171,700
Stephanie Rawlings-Blake Mayor (Mayor’s Office) $167,449
Mary Talley Executive Director III (Human Resources) $167,000
Rudolph Chow Director (Public Works) $166,500

Oddly, six of the ten employees with the highest gross pay are from the police department:

Name Title (Agency) Gross Pay
Stephen Nalewajko Jr Lieutenant (Police) $235,767
Anthony Batts Commissioner (Police) $210,705
Marc Camarote Sergeant (Police) $210,508
William Harris Jr Sergeant (Police) $207,614
Rhonda Johnson Paramedic (Fire) $205,999
Mark Walrath Lieutenant (Police) $194,655
Derrick Turrentine Paramedic (Fire) $193,532
Henry Raymond Executive Director III (Finance) $189,892
Albert Marcus Sr Officer (Police) $186,593
Kaliope Parthemos Executive Director V (Mayor’s Office) $183,085

Unfortunately, each government agency is further subdivided, creating a total of 673 sub-agencies. For example, the Department of Transportation contains a sub-agency representing their 305 crossing guards (median salary: $10,546). The large number of sub-agencies complicates meaningful comparisons; however, grouping them together by their parent agency and excluding those with less than ten employees results in 25 agencies, a more manageable number. This grouping can be visualized below:

baltimore_govt_agencies

Having aggregated the sub-agencies into their parent agency, it is now practical to compare them using a box plot. The “box” represents the middle half of all salaries (i.e. the range of salaries extending from the first to the third quartile). The vertical line within each box indicates the median salary, the point at which half of the salaries fall above or below. Loosely phrasing, the lines extending from the box represent salaries greater or less than those in the box, while the purple points represent ‘outliers,’ salaries that are either much higher or lower than the rest. Below is a box plot summarizing the annual salaries for each agency, ordered by their median:

baltimore_govt_salaries_2015

For some agencies, such as the State’s Attorney’s Office, there is a large difference between the highest salary and the next highest one (an outlier among outliers!). Below is a table of the highest and second highest salary, the later expressed as the difference from the highest salary, for each agency:

Agency Highest Annual Salary Next Salary
State’s Attorney’s Office $238,772 -$113,772
Police Department $211,785 -$65,685
Health Department $200,000 -$62,000
Transportation $176,015 -$61,005
Employee/Elected Officials Retirement Service $158,760 -$54,560
Finance $192,500 -$47,300
Fire and Police Retirement $155,300 -$43,800
Human Resources $167,000 -$42,000
Enoch Pratt Free Library $140,500 -$40,100
Planning Department $138,000 -$39,500
Civil Right and Wage Enfore $100,000 -$33,500
General Services $140,500 -$29,400
Department of Public Works $166,500 -$26,000
Law Department $166,500 -$26,000
Fire Department $171,700 -$25,200
Recreation and Parks $140,500 -$21,150
Comptroller $159,800 -$12,275
Mayor’s Office $178,900 -$11,451
Sheriff’s Office $114,050 -$10,307
Liquor License Board $95,700 -$6,187
Employment Development $134,800 -$4,800
Media Relations $160,000 -$2,800
Circuit Court $127,560 -$2,560
Housing and Community Development $154,000 -$2,100
City Council $110,908 -$31

Plotting these data suggested a negative correlation between the highest salary and its difference from the second highest one. In other words, as the highest annual salary increases, there is a larger difference between it and the next highest salary.

baltimore_highest_salaries_corr

One interpretation of these data is that they represent absolute differences between the two highest salaries rather than relative, or normalized, differences. For example, if the highest salary across agencies varies from $100,000 to $200,000 and the second highest salary in each agency is consistently 20% less, graphing their relationship in absolute differences produces the plot on the left below. However, if the data in this hypothetical example is normalized by dividing the second highest salary by the highest salary, the trend disappears, as illustrated by the plot on the right:

example_salaries_normalized

An identical transformation of the annual salaries, however, reveals that this interpretation does not explain the data because the same trend persists:

baltimore_highest_salaries_corr_normed

Below is a table of the highest and second highest salary, the later expressed as a normalized difference from the highest salary, for each agency:

Agency Highest Annual Salary Next Salary (% of highest)
States Attorneys Office $238,772 -47%
Transportation $176,015 -34%
Employee/Elected Officials Retirement Service $158,760 -34%
Civil Right and Wage Enfore $100,000 -33%
Police Department $211,785 -31%
Health Department $200,000 -31%
Planning Department $138,000 -28%
Enoch Pratt Free Library $140,500 -28%
Fire and Police Retirement $155,300 -28%
Human Resources $167,000 -25%
Finance $192,500 -24%
General Services $140,500 -20%
Department of Public Works $166,500 -15%
Law Department $166,500 -15%
Recreation and Parks $140,500 -15%
Fire Department $171,700 -14%
Sheriff’s Office $114,050 -9%
Comptroller $159,800 -7%
Liquor License Board $95,700 -6%
Mayor’s Office $178,900 -6%
Employment Development $134,800 -3%
Circuit Court $127,560 -2%
Media Relations $160,000 -1%
Housing and Community Development $154,000 -1%
City Council $110,908 < -1%

Finally, a somewhat different plot can highlight unique features of an agency. Below are violin plots of the annual salaries for the Police, Fire, Sheriff and Law Department. In these plots, the width reflects the probability of salaries corresponding to each annual salary. The ‘lumpiness’ seen for the Police, Fire and Sheriff’s Department presumably reflect step-wise increases in pay grades. In contrast, salaries within the Law Department are more continuous with no discernible structure, as seen below:

baltimore_fire_sheriff_police_law_salaries_2015

That’s it for this post. Please stay tuned for the next one!

Reproducibility