The assumption that ownership has an effect on the diversity of news is based on the forms of control that ownership allows and the market conditions in which ownership is exercised. In this study, we perform a large-scale analysis of the Swedish newspaper market, surveying 130 newspapers and parliamentary speeches over a period of six years (2014-2019), to substantiate to what extent market and for-profit ownership forms impact political viewpoint diversity. Our analysis shows that newspapers with market leadership and chain ownership offer more political viewpoint diversity than number two and single-owned papers. In contrast, the ownership forms surveyed here (private, foundation, and publicly traded ownerships) display little effect on newspapers' internal diversity. We also find that a greater number of papers in a local market does not imply more external diversity in that market. The analysis thus offers some nuance to the notion that ownership form and market pluralism are prerequisites for viewpoint diversity, highlighting instead the importance of scale effects for pluralistic media systems.