Advertising is a critical competitive tool that shapes interactions among firms in the product market. Using third-party tracked data on advertising outlet costs, I find that a nontrivial portion of public firms, even those with intense advertising activities, do not disclose advertising expenses in their financial statements, indicating significant disclosure discretion. I further use product category-level advertising data to develop a firm-specific measure of advertising rivalry. I predict and find that advertising rivalry is negatively associated with the likelihood of disclosing advertising expenses. This negative association is more pronounced when firms advertise on less trackable media outlets or have more mature products. These findings suggest that firms consider their advertising expenses proprietary and that concerns about advertising competition discourage the disclosure of advertising expenses.

广告是一种重要的竞争工具，可以塑造产品市场中公司之间的互动。使用关于广告渠道成本的第三方跟踪数据，我发现相当一部分上市公司，即使是那些广告活动密集的公司，也不会在其财务报表中披露广告费用，这表明有很大的披露自由裁量权。我进一步使用产品类别级别的广告数据来制定公司特定的广告竞争衡量标准。我预测并发现广告竞争与披露广告费用的可能性呈负相关。当公司在不易追踪的媒体渠道上做广告或拥有更成熟的产品时，这种负面关联会更加明显。