<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"><channel><title>Duc Nguyen — Writing</title><description>Retention marketing, ecommerce operations, and the data underneath.</description><link>https://duc.work/</link><language>en-us</language><item><title>Your SMS cost data is probably wrong, and your ROI is wrong with it</title><link>https://duc.work/en/writing/your-sms-cost-data-is-probably-wrong/</link><guid isPermaLink="true">https://duc.work/en/writing/your-sms-cost-data-is-probably-wrong/</guid><description>A warehouse table quietly dropped 25 of 31 days for one store. Every cost number built on it was understated for two months before anyone checked.</description><pubDate>Tue, 15 Sep 2026 00:00:00 GMT</pubDate></item></channel></rss>