This dissertation reports on a multi-dimensional longitudinal investigation of the factors that influence Enterprise Architecture (EA) diffusion and assimilation within the U.S. federal government. The study uses publicly available datasets of 123 U.S. federal departments and agencies, as well as interview data among CIOs and EA managers within select Federal Government agencies to conduct three multi-method research studies: 1) a qualitative study to investigate organizational and institutional factors that enhance or impede EA assimilation at program level; 2) a quantitative study to examine the antecedents of EA assimilation at adopter unit level and 3) a longitudinal quantitative study to examine: 1) the antecedents of EA assimilation within adopter populations as marked by prominence within each of the EA assimilation phases 2) the influence of sudden changes in environmental (institutional) context on the EA assimilation process; and 3) the determinants for each EA assimilation stage. I use time-lagged partial least square, ordinary least square and multinominal logistic regression to analyze these effects. The study shows that an innovative leadership style is the key to advancing EA program assimilation within adopter units. Framing and labeling of an EA program as an administrative driven innovation or reform as opposed to a business essential strategic tool greatly influences its value perception, adoption and assimilation. Institutional coercive pressure is not a long term sustainable strategy in driving EA assimilation, though it has a “jolt” like short term effect in accelerating assimilation. EA assimilation has distinct micro and macro level antecedents. Factors also have "differently-directioned effects," that is factors that promote EA progress at certain assimilation phases and stages inhibit progress at other phases and stages. Changes in the temporal environmental context have “factor elasticity” effect on the explanatory power of the antecedents. That is, antecedents lose and regain their explanatory power commensurate with changes in the environment over time.
Overall, the study’s findings have several major implications for policymakers: 1) complex administrative innovations such as EA require strategic frameworks as opposed to blueprints to 1) overcome dynamic complexity and 2) drive multi-level assimilation; 2) EA assimilation at each of the levels have different sets of definitions and antecedents 3) each of the levels have different properties and characteristics and require different approaches and strategies, 4) institutional coercive pressure is only effective when applied as a temporal strategy, 5) individual EA program and adopter unit assimilation are interdependent. That is, successful assimilation of EA within the organization is highly dependent upon the degree of embracement and legitimization of individual EA programs.