2.1 Research Focus
In order to identify the fields11 in which a state has a comparative advantage in research, this report looks at two indicators—relative volume and relative impact—along two dimensions. First, a state’s performance in a given research field was compared to its own performance in other research fields. For example, how does Colorado’s research in environmental science compare to its research in medicine? Second, a state’s performance in a given research field was compared to other states’ performances in the same research field. For instance, how is Colorado’s research in environmental science relative to Maryland’s research in environmental science?
Analogous to the location quotient for an industry, the relative volume of a state’s research output in a field takes into account the total amount of research that a state produces.12 A value above 1.00 indicates that the state produces a higher proportion of its research output in that field than the national average and vice versa. For example, even though research in agricultural and biological sciences comprise only 8.4 percent of Alabama’s total research output from 2004 to 2013, the state’s relative volume in this field of 1.18 indicates that its output is 18 percent higher than the national average.
As mentioned in the previous section, the field-weighted citation impact provides a normalized measure of
citation counts.
Both the relative volume and the field-weighted citation impact of research output enable comparisons across different research fields.
For consistency, in all subsequent figures that use indicators across fields, those fields are arranged in a way such that those closely related to each other are placed next to each other on the axis or along the edge of the chart.13
This section provides in-depth case studies of several states that have distinct comparative advantages in various research fields. It is not meant to be a comprehensive report of every state’s research strengths, but rather an outline of the process by which one can use different indicators to identify and showcase such strengths.

Figure 2.1—U.S. Research Output by Fields as Percentage of Total U.S. Output, 2004–2013. Source: Scopus®

National Measures
To understand and better appreciate in which fields certain states have a comparative advantage over others, it is important to have a sense of in which the fields in which the U.S. excels as a whole. As Figure 2.1 shows, from 2004–2013, 28.7 percent of the country’s total research output—or about 1.4 million publications—was in medicine. Engineering and biochemistry, genetics and molecular biology were the two fields with the next highest levels of research output at 17.4 percent and 15.4 percent respectively. Within medicine, the top 3 states in terms of relative volume were: Minnesota, Rhode Island and North Caroline. Within engineering, the top 3 states in terms of relative volume were: New Mexico, Idaho and Virginia. Within biochemistry, genetics and molecular biology, the top 3 states in terms of relative volume were: Maryland, North Carolina and Nebraska.
Relative to the total world output, the U.S. produced a particularly high relative volume of research in psychology (3.6 percent of total U.S. research output compared 2.2 percent of total world output) and neuroscience (3.8 percent of total U.S. research output compared to 2.5 percent of total world output).
As Figure 2.2 shows, the relative citation impact of the total U.S. research output tended to be well above the world average across all fields. The fields in which the U.S. achieved the highest field-weighted citation impacts are: computer science (1.74); materials science (1.62); economics, econometrics and finance (1.62); arts and humanities (1.61); and chemistry (1.61). For all of these areas, Massachusetts was among the top four states in terms of field-weighted citation impact.

Figure 2.2—Field-Weighted Citation Impact of U.S. Research Output, by Field, 2004–2013.
Source: Scopus®

 
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