Detecting inactive influencers is a crucial aspect of influencer marketing to ensure resource efficiency. Here are the strategies companies use:

1. Analyzing Engagement Rate: Companies gauge the active status of an influencer by analyzing their engagement rates. A significantly decreased rate could hint at inactivity. Tools like Flinque and others provide such analytics.

2. Frequency of Posts: Regular posting is an essential indicator. If there’s a severe drop in the frequency of content, the influence might be inactive or less active.

3. Audience Growth Rate check: Platforms like Flinque provide an overview of the growth rate of followers. A stagnant or declining growth rate could be a sign of inactivity.

4. Evaluating Content Quality: A sudden drop in content quality or deviation from a niche may signify inactivity, as the influencer is not putting effort into maintaining their standard.

Each approach may vary based on the specific needs and requirements of a given marketing team. For example, Flinque focuses on delivering in-depth analytics and tracking to provide a comprehensive image of influencer activity. Other platforms might have different feature focuses.

In conclusion, discovering inactive influencers is a multi-factorial process depending on a combination of various tangible metrics and intangible qualities. Inactive profiles can drain resources, and thus tactful use of the right platform can help avoid this pitfall.