Before settling on the Cosine estimate for Chapter 6 and 7, I experimented with using Correspondence Analysis to examine the party platforms. Correspondence Analysis is an exploratory dimensional scaling routine that has been used to examine textual data. A central reason for running this analysis was to discover whether a consistent ideological dimension of language separated the two parties over time. If the dominant patterns in platform language are ideological, Correspondence Analysis should easily identify consis- tent inter-party differences. On the other hand, if ideology is only one of many patterns in the data, exploratory factor analysis should report the presence of other salient struc- tures of variance. While the method is exploratory, we have a good sense what we’re looking for. For instance, one would expect ideological differences to have increased over the past 20 years as partisans have polarized more deeply and on more issues. Most measures of polarization show increasing ideological differences between the two parties since the 1970’s and, if the dominant structure in platform language is ideology, factor analysis should pick up on that pattern. To maximize the potential of finding consistent ideological differences in party language, I limited the analysis to platforms from 1948 on. Many of the core ideological antagonisms have been consistently present since WWII (e.g. size of government), so focusing on recent platforms gives ideological differences the best chance of emerging from the data.
Figures 3.1 through 3.6 report estimates of platform location along the six most im- portant dimensions identified by Correspondence Analysis. Most of these dimensions are difficult to interpret substantively but the presence of well-organized empirical patterns in the data point to the presence of more structure than ideological differences could capture. Moreover, most of these dimensions look nothing like what we would expect to
see in a measure of party ideology, further evidence that ideological differences are being overwhelmed by other types of variance.
Year 1st Dimension Estimate −1 0 1 1948 1952 1956 1960 1964 1968 1972 1972 1980 1984 1988 1992 1996 2000 2004 Democratic Platform Republican Platform
Figure 3.1: Correspondence Analysis 1st Dimension Platform Location: 1948-2004
The first dimension that Correspondence Analysis extracted is, more or less, time. Figure 3.1 shows where the two parties’ platforms fell on this dimension from 1948 to 2004. Clearly, this dimension captures the change in language that is present in both parties’ platforms over the last half-century. The Democratic platform of 2004 is much more similar to the Republican counterpart from the same year than it is with Democratic platforms from 10 or twenty years earlier. This fact holds true for the Cosine estimates that are used in Chapters 6 and 7. As a general rule, the Democratic and Republican platforms from the same election have more in common with each other than with their own platform from other elections. This finding is reinforced by most of the dimensions shown below and many of the others that were not included.
The fourth dimension identified in this exercise is the only one that bears any resem- blance to left-right ideology as we understand it. From the end of the Second World War to the early 1970’s, the parties were relatively close to each other and they have become
Year 2nd Dimension Estimate −1 0 1 2 3 1948 1952 1956 1960 1964 1968 1972 1972 1980 1984 1988 1992 1996 2000 2004 Democratic Platform Republican Platform
Figure 3.2: Correspondence Analysis 2nd Dimension Platform Location: 1948-2004
Year 3rd Dimension Estimate −2 −1 0 1 2 1948 1952 1956 1960 1964 1968 1972 1972 1980 1984 1988 1992 1996 2000 2004 Democratic Platform Republican Platform
Year 4th Dimension Estimate −2 −1 0 1 2 1948 1952 1956 1960 1964 1968 1972 1972 1980 1984 1988 1992 1996 2000 2004 Democratic Platform Republican Platform
Figure 3.4: Correspondence Analysis 4th Dimension Platform Location: 1948-2004 more distinct over the following 30 years. This is one of the only dimensions that show consistent differences between the two parties, and the only dimension where the differ- ences are pronounced across the entire period. The fact that Correspondence Analysis did identify a pattern that vaguely resembles ideology indicates that the tool does pick up on consistent inter-party variance, where it exists. If nothing resembling ideology had emerged from this exploration of the data, it simply could be due to using the wrong tool. However, this dimension indicates that Correspondence does identify consistent dif- ferences between Democrats and Republicans language where they are present. Thus we have even more confidence that these are not the only, or even most important, patterns in the data.
Figures 3.5 and 3.6 show the dimensional scores for the fifth- and sixth-most important Correspondence Analysis dimensions. These are included to reinforce the points made already: multiple distinct patterns in the data and a great deal of similarity between the two parties. Regardless of the substantive interpretability of these mathematical dimensions, it is striking how often the two parties change in the same ways over time.
Year 5th Dimension Estimate −2 −1 0 1 1948 1952 1956 1960 1964 1968 1972 1972 1980 1984 1988 1992 1996 2000 2004 Democratic Platform Republican Platform
Figure 3.5: Correspondence Analysis 5th Dimension Platform Location: 1948-2004 Whatever evolutions in substance or tone have happened over the last fifty years, the two parties have changed their language in many of the same ways.
I am not arguing that ideology is meaningless or irrelevant; it is clearly impor- tant. However, when we analyze party language, ideological differences capture a limited amount of the systematic variance in the data. If we insist on forcing these data onto a single dimension, we ignore much of what is going on. Even in a best case time-period, stable inter-party differences share the field with many other systematic patterns in how the parties articulate themselves. If the scope of analysis is broadened to include the last 150 years of political history, there are no inter-party differences that persist for the entire period. The final section pushes this case one step farther by reporting a failed attempt to measure ideological location from platform language in the way that is commonly done in political science.
Year 6th Dimension Estimate −2 −1 0 1 2 1948 1952 1956 1960 1964 1968 1972 1972 1980 1984 1988 1992 1996 2000 2004 Democratic Platform Republican Platform
Figure 3.6: Correspondence Analysis 6th Dimension Platform Location: 1948-2004