What is the key difference between impression share and tap share in Apple Search Ads, and how should each metric inform your bidding strategy?

In Apple Search Ads, impression share and tap share are two distinct metrics that provide insights into your ad's visibility and performance, and they should inform your bidding strategy differently. 'Impression share' represents the percentage of times your ad was shown when it was eligible to be shown for a given keyword or search term. It indicates how often your ad is competing effectively for available impressions. A lower impression share suggests your bid may be too low, your creative relevance is lacking, or your budget is too restrictive, causing you to miss opportunities to display your ad. 'Tap share', on the other hand, represents the percentage of times users tapped on your ad when it was shown. It reflects the effectiveness of your ad creative and its ability to attract clicks from users who saw it. A low tap share suggests your ad creative (icon, screenshots, ad text) is not compelling enough, or your ad is being shown to an audience that is not relevant to your app. Impression share should inform your overall bidding strategy. If your impression share is low, it suggests you need to increase your bid to compete more effectively for available impressions. Tap share should inform your creative optimization strategy. If your tap share is low, it suggests you need to improve the relevance and appeal of your ad creative. By monitoring and optimizing both metrics, you can improve the overall performance of your Apple Search Ads campaigns. If your tap share is high and impression share low, increasing bids makes sense. However, a low tap share might indicate poor creatives that should be addressed before simply increasing bids.