When I optimize a PPC account one of the first places I look is the mobile vs desktop data. For e-commerce sites the conversion rate on mobile devices can be less than half of the conversion rate on desktops. If you're in that situation and you aren't lowering your mobile bids you are losing money for mobile devices. Here is how you can check your mobile conversion rate:
1) Go to the campaigns page.
2) Choose "Devices" from the "Segment" drop-down menu.
3) You can analyze results for each campaign or scroll to the bottom of the page and look at the account as a whole. Make sure your time range is long enough that you have enough data to make smart choices. You should have at least 30 conversions to be able to make a smart decision.
4) Note the difference in conversion rate between desktops and mobile.
5) You can make mobile bid adjustments on the campaign settings page. The mobile bid adjustment is based off of the desktop bids. If your conversion rate on mobile is half as high as on desktops you should make the bid adjustment -50% and all your mobile bids will be half of your desktop bids.
If you haven't checked your mobile conversion rate out recently this is a good way to give your PPC performance a boost!