{'fraction_non_alphanumeric': 0.021233569261880688, 'fraction_numerical': 0.007077856420626896, 'mean_word_length': 5.387096774193548, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Studies of Trends in Third-Party Logistics Usage: What Can We Conclude?


 This article evaluates the various longitudinal studies of third-party logistics (3PL) usage and proposes methods and approaches to improve the rigor of future research in this area. Three well-established methodologies for combining the results of multiple studies are reviewed (literature reviews, meta-analysis, and repeated survey analysis), and then considered in application to the findings of the various 3PL usage studies since 1991. Beginning with an overview of the results that emerge from simply combining and comparing the key longitudinal data, the article moves on to a more detailed analysis of the measurement scales, data collection methods, and samples utilized in the different 3PL surveys. The article ends with concrete recommendations for reorienting the ongoing surveys to increase their rigor and validity, and thus increase their predictive value to both academics and logistics managers.