To be able to make broad statements about the effectiveness of biodiversity mainstreaming, ideally one would need to start with a set of core indicators which are fairly easy and inexpensive to collect, and which are comparable across countries. A few other indicators may also merit further consideration. Selecting a core set of indicators (Step 6) is an important element of this, and aims should be made for these to be as consistent as possible across countries, so as to enable aggregation of data at regional and global levels.