I'm not so sure what you mean by "measure the power of the state in the objective way", it is nearly impossible to measure intangible factors with hard numbers. Quantification of power is, nevertheless, a critical issue and there are a variety of studies and indexes measuring national power.
I'll start with an introduction of sorts, hoping to give you a lot more buzzwords to help you with your research, follow with a brief description of two metrics (CNP & CINC) I'm a tad familiar with and close with every relevant study/metric I could find from non partisan institutions.
General approaches to measuring power
There are several approaches to measuring power, and they generally increase in complexity over time. The earliest model I know of is the one devised by F. Clifford German in A Tentative Evaluation of World Power:
national power = N(L + P + I + M)
N is nuclear capability, L is land, P is population, I is the industrial base and M is military size
Several models followed German's model1, including the CINC (more on that later), that first appeared in 1972. In 1976, Jeffrey Hart, attempted to define the general approaches to measuring power, in Three approaches to the measurement of power in international relations. In very general terms his approaches are:
Control over events and outcomes
Hart argues that there's no reason to believe that the degree of control over resources is directly proportional to the degree of control over events. A simplistic example of that is the current financial crisis, nations have only partial control over the recovery of the world economy, yet the recession is consequential for all.
Hart considers the approach superior to the other two, as it takes into account interdependence and collective action.
Control over resources
The more common approach that argues that control over a set of tangible and intangible resources translates to control over actors and events and outcomes. The main challenges of the approach is that it's not always certain that actors will be able to use all their resources, intangible resources (e.g. leadership skills, will to use force) are extremely difficult to quantify, and predicting different outcomes demands measuring different combinations of resources.
Control over actors
This approach is based around Robert Dahl's definition of power:
“A” getting “B” to do what “A” wants.
The approach largely assumes a deterministic relationship between "A" and "B", ignoring more complicated scenarios where, for example, "A" acts in a way that limits "B"'s range of possible actions.
Adding to the complexity, these and later approaches, are usually coupled with two major analytical approaches:
- Top down, with international factors being weighted more than national ones, and
- Bottom up, with national factors being weighted more than international ones.
Furthermore, and depending on the desired outcome, metrics may be:
- Inclusive (large and diverse set of factors), when aiming at large scale comparisons, or
- Exclusive (very narrow and specific set of factors), when aiming at predicting very specific events or actions.
I think it quickly becomes clear that several distinctly different metrics may be appropriate, depending on what exactly your definition of power is and what exactly you are trying to measure and/or predict. Given that this isn't entirely clear from your question, I'll stop the introduction here and move on to two current metrics.
1 Search for Wilhelm Fucks, Norman Alcock and Ray Cline (for example)
Comprehensive National Power
The CNP is a Chinese concept and it measures both hard and soft powers. It's a very inclusive metric, taking into consideration natural resources, population, economic performance, scientific technology, politics, military power, culture, and education. You can find a thorough explanation of the methodology employed in the fifth chapter of Michael Pillsbury's China Debates the Future Security Environment. For posterity, these are the weighted factors presented in the book:
National Power Factor Weighted Coefficient
Total CNP 1.00
Natural resources 0.08
Economic activities capability 0.28
Foreign economic activities capability 0.13
Scientific and technological capability 0.15
Social development level 0.10
Military capability 0.10
Government regulation and control capability 0.08
Foreign affairs capability 0.08
It should be noted, however, that there appears to be disagreement within China over measurements of CNP1:
In addition to the afore-mentioned political reasons, disagreement over measurement remains a major reason causing differences in estimations of China's power status. To date, more than 10 evaluation and measurement methods have been in use in the field, with basically all using a different type of index. The measuring methods used in assessing China's power status have become increasingly complicated. There are neither common standards for measuring nor continuity in methodology development. The differences in measurement appear for many reasons, though we will focus only on a selection of measurements used to study China's comprehensive state power. For instance, scholars at Tsinghua University of Beijing classify the factors of comprehensive state power into eight categories and 23 indices, while their peers in China Academy of Social Sciences use eight categories and 64 indices; scholars in the Academy of Military Sciences of the People's Liberation Army (PLA) have developed a seven-category system which consists of 29 secondary indices and over 100 tertiary indices; and analysts in the China Institute of Contemporary International Relations have proposed a seven category, 115 basic indices scheme in their measurements.Due to the lack of a common standard, neither increasing the number of factors measured, nor using complicated measurements have led to an improvement in the accuracy of measuring China's current power status.
- The Rise of China and its Power Status, The Chinese Journal of International Politics.
Composite Index of National Capability
CINC is a hard powers statistical measure, a linear index of capabilities focused on national assets, that's part of the Correlates of War project1:
This measure is generally computed by summing all observations on each of the 6 capability components for a given year, converting each state's absolute component to a share of the international system, and then averaging across the 6 components.
The 6 components are:
- Military personnel (thousands)
- Military expenditures (For 1816-1913: thousands of current year British Pounds. For 1914+: thousands of current year US Dollars.)
- Iron and steel production (thousands of tons)
- Primary energy consumption (thousands of coal-ton equivalents)
- Total population (thousands)
- Urban population (population living in cities with population greater than 100,000; in thousands)
and CINC's definition of power is2:
"Power" - here defined as the ability of a nation to exercise and resist influence - is a function of many factors, among them the nation's material capabilities. Power and material capabilities are not identical; but given their association it is essential that we try to define the latter in operational terms so as to understand the former.
Most of Correlates of War data sets are available online.
- National Material Capabilities (v4.0)
- Correlates of War Project National Material Capabilities Data Documentation Version 4.0
Related studies & metrics