In 1997, a meta-analysis on the relationship between secondhand smoke exposure and lung cancer concluded that such exposure caused lung cancer. The increase in risk was estimated to be 24% among non-smokers who lived with a smoker. In 2000, Copas and Shi reported that there was clear evidence of publication bias in the studies included in this meta-analysis. They further concluded that after correcting for publication bias, and assuming that 40% of all studies are unpublished, this increased risk decreased from 24% to 15%. This conclusion has been challenged on the basis that the assumption that 40% of all studies are unpublished was "extreme". In 2006, Takagi et al. reanalyzed the data from this meta-analysis to account for publication bias and estimated that the relative risk of lung cancer among those exposed to secondhand smoke was 1.19, slightly lower than the original estimate. A 2000 meta-analysis found a relative risk of 1.48 for lung cancer among men exposed to secondhand smoke, and a relative risk of 1.16 among those exposed to it at work. Another meta-analysis confirmed the finding of an increased risk of lung cancer among women with spousal exposure to secondhand smoke the following year. It found a relative risk of lung cancer of 1.29 for women exposed to secondhand smoke from their spouses. A 2014 meta-analysis noted that "the association between exposure to secondhand smoke and lung cancer risk is well established."