OSM for change detection

Historic OSM data is available but if a city has 10% more buildings in OSM today than a year ago then you cannot know whether these 10% are actually new buildings that have been created on the ground, or just buildings that were not mapped before and are mapped now (but could have been there for the last 100 years). So your plan would really only work in areas where data is practically complete AND the local community is so active that changes are added in a timely manner. This will only be the case in a few regions and at the very best for the last 3-4 years.