The stalling of WTO multilateralism and the proliferation of preferential trade agreements in recent decades have drawn substantial attention to the impacts of preferential liberalization. A critical question is how they affect the trade barriers imposed against outsiders. I examine the relationship between preferential trade liberalization and protection against non-member countries by testing the predictions of a political–economy model based on the previous literature. Focusing on a specific model allows me to uncover the mechanisms via which preferential liberalization affects external import protection, whereas most of the existing literature has focused on establishing the sign of the effect only. Furthermore, I focus on not only tariffs, as most studies do, but also on the temporary trade barriers of antidumping and safeguards. I test the predictions for Latin America and obtain results that provide solid evidence supporting two mechanisms from the theory, which lead to lower protection against non-members of a preferential trade agreement. First, a lower preferential import protection level means that the increase in preferential imports from increasing the external tariff creates a smaller increase in tariff revenue. Second, as preferential import protection is cut, there is a decrease in the markup and sales of domestic firms, and thus raising the external import protection generates less profit. Moreover, this second effect is present when the political motivation of the government is sufficiently strong.

We describe here an algorithm for distinguishing sequential from nonsequentially folding proteins. Several experiments have recently suggested that most of the proteins that are synthesized in the eukaryotic cell may fold sequentially. This proposed folding mechanism in vivo is particularly advantageous to the organism. In the absence of chaperones, the probability that a sequentially folding protein will misfold is reduced significantly. The problem we address here is devising a procedure that would differentiate between the two types of folding patterns. Footprints of sequential folding may be found in structures where consecutive fragments of the chain interact with each other. In such cases, the folding complexity may be viewed as being lower. On the other hand, higher folding complexity suggests that at least a portion of the polypeptide backbone folds back upon itself to form three-dimensional (3D) interactions with noncontiguous portion(s) of the chain. Hence, we look at the mechanism of folding of the molecule via analysis of its complexity, that is, through the 3D interactions formed by contiguous segments on the polypeptide chain. To computationally splice the structure into consecutively interacting fragments, we either cut it into compact hydrophobic folding units or into a set of hypothetical, transient, highly populated, contiguous fragments (“building blocks” of the structure). In sequential folding, successive building blocks interact with each other from the amino to the carboxy terminus of the polypeptide chain. Consequently, the results of the parsing differentiate between sequentially vs. nonsequentially folded chains. The automated assessment of the folding complexity provides insight into both the likelihood of misfolding and the kinetic folding rate of the given protein. In terms of the funnel free energy landscape theory, a protein that truly follows the mechanism of sequential folding, in principle, encounters smoother free energy barriers. A simple sequentially folded protein should, therefore, be less error prone and fold faster than a protein with a complex folding pattern.