We strongly advocate for Tobacco 21 legislation and, in November 2018, we stopped selling non-tobacco and non-menthol-based flavored JUULpods to traditional retail stores, which represented 50% of our revenue at that time. In addition, we enhanced our online age-verification, strengthened our retailer compliance by conducting over 2,000 secret shopper visits a month, shut down our Facebook and Instagram accounts and work constantly to remove inappropriate social media content generated by others. We also continue to develop technologies to further restrict underage access with our retailer partners and distributors. These actions, however, have not been followed by others in the industry and by those selling counterfeit or compatible products.
We do not want or need non-nicotine users. Our market is the over 1 billion adult smokers worldwide who should have the opportunity to switch to vapor products if they so desire. We are seeing tremendous success so far. In a recent behavioral study undertaken by third-party researchers sponsored by the company, we have seen that nearly half of adult smokers who purchase and use JUUL products switch completely from smoking cigarettes within three months, with the rate of complete cigarette abstinence increasing over time.
We also believe our products are driving a historic reduction in the consumption of combustible cigarettes. As JUUL products have gained market share among adult smokers, cigarette sales have declined at an accelerating rate. In 2018, cigarette sales declined at an average of 5% year-over-year, the fastest rate of decline in a decade, according to IRI data which tracks retail sales. In 2019, IRI data show cigarette sales plummeting at more than 8% year-over-year through May. To put that in context, every 1% decrease in the smoking rate translates to 125 million packs of cigarettes that are never sold or smoked.