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Based on the searches, I have solid material: USA.gov/CFPB/FTC/Federal Reserve guidance, Experian average debt data, Citi utilization guidance, credit score improvement timelines, and Bank of America secured card details. Now let me write a comprehensive SEO article in English for the US, about improving credit score, with the required structure: intro, body (with a table), and action guide. Following constraints: no fabricated data, vague cost descriptions where uncertain, no emojis/slang, max 3 heading levels, natural tone, no banned words, keywords woven in naturally.