English: Chart showing number of sanctioned perfect ("300") games by year in ten-pin bowling, both by raw numbers of perfect games, and numbers of perfect games per sanctioned league bowler

• Source for raw numbers of sanctioned perfect games: Hatfield, Ron; Freeman, James. Number of Sanctioned 300 Games by year (October 16, 2017). Archived from the original on October 13, 2023. (Bowling Beyond the Basics)
• Freeman and Hatfield posit that the increase in perfect games is due to factors such as the introduction of reactive resin coverstocks, asymmetric ball cores, synthetic lane surfaces, and precision lane oiling machines.
• Data listing and sourcing for number of sanctioned league bowlers is presented at File:1997- USBC membership and lanes and centers NORMALIZED.png (expand collapsible text).
• Increase in games-per-bowler is largely due to declining league participation.
• Source for number of league bowlers in 1980 is Bowling Through The Decades: The 1980s. PBS (Independent Lens) (2007). Archived from the original on March 9, 2007.
• Notes re Version 1: Raw numbers from Freeman and Hatfield. League bowler count, 1997-, per USBC. Dotted line based on linear interpolation of bowler count from 1980 (8M, per PBS) to 1997 (4.41M, per USBC).
• Technical note: most SVG code was automatically generated by the "Line charts" spreadsheet linked at User:RCraig09/Excel to XML for SVG. Minor additions and adjustments were made in a text editor.

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