Pakistan's tax-to-GDP ratio (historically around 9–11%) is explained by a confluence of factors: (1) heavy reliance on indirect taxes (sales tax, customs duties) rather than broad-based direct taxes; (2) constitutional and political exemptions for agriculture, despite its large economic size; (3) a large undocumented informal economy estimated at 35–40% of GDP; and (4) weak FBR enforcement, narrow withholding tax net, and rampant tax evasion by powerful sectors.