Health Care reform has been a hot topic where statistics have been used to: Abuse anecdotal math to falsify the truth and truthify falsehood.
(This is the sixth of the series on misuse of statistics. For the earlier postings, click: 1-Going to St. Ives, 2-Playing Percentages, 3-Correlation and Causation, 4-Fun with the Normal Curve, 5-Global Warming.)
In a December 2009 posting, I pointed out that the map of per capita Medicare spending by county in the US looked a lot like the political division between the "Blue Counties" (Democrats, L-Minds) and the "Red Counties" (Republicans, C-Minds).
Since counties are so numerous and therefore confusing, I used Congressional Budget Office 2004 statistics of per capita Medicare spending on a statewide basis to show that the top five Highest Spending States tended to be Blue States and the top five Lowest Spending States tended to be Red States.
(My stated purpose -agenda if you like- was to indicate that Liberals consume an outsized share of the common pot of health care resources, as compared to Conservatives who take a smaller piece of the pie per capita.)
The figure above shows the CBO bar graph that orders the states by raw Medicare Spending per capita, from lowest (Utah) at the top to highest (Massachusetts) at the bottom. The box on the right is a magnification of the top and bottom of the bar graph. As indicated, the lowest spending states have consumed $4,000 to $4,800 per beneficiary. The highest spending states consumed $6,300 to $6,700 per capita. [Click on figure for a larger version.]
I consider the above to be a good, clear use of statistics. The bar graph, however, is a bit misleading. Notice that the horzontal axis does not start at $0, but rather at $3,500, which is visually misleading because it seems to show that the highest spending states consume over twice as much as the lowest spending. Actually, they consume only about 150% as much.
Lesson Learned: When viewing graphs, be very suspicious when the axes do not start at zero.
In a comment, Howard* provided a link to Hopson and Rettenmaier (NCPA) that, it seemed to him, "... finds high cost states are Louisiana, Maryland, Oklahoma, Texas, Kansas, and low cost states are New York, Vermont, New Mexico, Virginia, Iowa. That’s closer to the opposite correlation."
Indeed, on page 37 of NPCA, as shown in the figure below, they do identify the ten states listed by Howard as the five "Low-Cost States" and five "High-Cost States". The NCPA study is based on the exact same Medicare data from 2004/2005. What is going on??? [Click on figure for a larger version.]
The figure above uses the CBO bar graph and shows that the NCPA list does not match at all. New York for example, is listed as a "Low-Cost State" by NCPA but, acording to the CBO bar graph, it is the third highest cost! Texas, on the other hand, that is sixth on the CBO list, indicating low cost, is listed as a "High-Cost State" by NCPA! Yikes!
Part of the answer is in the caption of the NCPA Table VII: "Summary of High- and Low-Cost States After Adjusting for Observable County Differences" Oh, this is not raw data but it has been ADJUSTED.
OK, how was it adjusted? That is not obvious without reading the whole report. They have taken the following into account: "Percent Black", Percent Hispanic", "Percent Female". Each of these factors tend to lean heavily Democratic in their voting patterns, indicating they tend to be L-Minds.
So, NCPA has adjusted the data to reduce the apparent costs in states with Democratic constituencies and effectively increase the apparent costs in states with Republican consitituencies. (Of course NCPA would say they are adjusting for clear patterns of medical need. Blacks, Hispanics and Females seem to need - or at least consume- more medical care than Males and non-Minorities on a per capita basis.)
The above adjustment could be described as reasonable and scientific. Some identifiable groups do need more health care for good reasons that are not their fault. However, NCPA has done some other adjusting that is totally absurd, tricky, and non-scientific. Read on!
Notice the header on the second column: "% of Counties in the Top Quintile". They have treated counties equally even though they vary greatly in population!
For example, I was born in Kings County (Brooklyn, NY) which has a population of 2,556,598. My professional life was spent in Tioga County (Newark Valley and Apalachin, NY) which has a population of 50,171. So, in computing that New York is a "Low-Cost State" they count Kings County and Tioga County equally, even though the ratio of their populations is over 50 to 1 !!!
Comparisons of spending for government programs should always be done based on the per capita statistics. CBO compares states and counties on a per capita basis. NCPA clearly has an agenda because they figure "Low-Spending States" on the basis of the percentage of counties in the highest and lowest quintiles. What a crock!
That is like a "50/50 Horse and Rabbit Stew, one Horse and one Rabbit".
Lesson Learned: Be very suspicious of "adjusted" data, especially when the person or group doing the "adjusting" has a particular agenda.
*I have the highest respect for Howard's grasp of scientific matters in general, and statistics in particular. I do not fault him for being led astray by the NCPA's statistical manipulations. They were far from obvious and NCPA seems to have taken special care to hide what they did (while remaining on the right side of "truth" by revealing their machinations in the "fine print").