Margolis, who analyzes all international agreements concluded from 1943 to 1977, provides empirical support and finds that the distribution of seats in the Senate is very predictable between the treaties and the executive agreements of Congress. Footnote 48 The findings form the basis of the circumvention hypothesis that the choice between contracts and executive agreements is exclusively the function of national legislative assistance. Figure 4 shows estimated coefficients and confidence intervals of 95 percent for all x over the range [0, 0.1]. Even under the strict assumption that the shortest 10% of executive agreements are exclusive executive agreements, there is still a substantial difference between the treaties and the executive agreements of Congress, which is statistically different from 0. This article is based on an analysis of the survival period and shows that contracts are more sustainable obligations than executive agreements. In particular, there was a 15% probability that a standard contract concluded in 1982 failed until 2012, compared to a 50% probability that it would fail as an executive contract. The results are consistent with the fact that treaties remain an important political instrument for the United States, as they are a qualitatively different promise from a promise made in the form of an ex ante agreement between Congress and the executive branch. Now let`s look at the case of executive agreements alone. As noted above, the TIF does not distinguish between the executive agreements of Congress, although the estimated share of the first agreements is between 5 and 6% of all agreements. To take into account the fact that some international instruments are exclusive executive agreements that should be excluded from the analysis, this study uses a sensitivity analysis.
Footnote 102 Table 4 gives results for cox`s model. The model (1) contains only the contractual indicator. It can be seen as a simple descriptible comparison of the sustainability of contracts and all executive agreements, without taking into account other characteristics. The model (2) includes the chair and the theme of fixed effects. They indicate the average difference in sustainability, given that two agreements were concluded by the same president and in the same discipline. The model (3) also contains fixed country effects. Footnote 99 If the choice between executive treaties and contracts was the result of a historical dependence irrelevant to the current content, there should be no difference in the permanence of treaties and executive treaties if all of these characteristics are maintained constantly. The contractual coefficient should therefore be small and statistically insignificant. Model (4) new controls for the part of the presidential party`s seat in the Senate, as well as for a divided government to examine whether differences between treaties and executive agreements are declared by a president`s intention to bypass the Senate.