The trend of disabling tracking makes it harder for firms to rate the effectiveness of campaigns, Starcom managing partner Paul Kasamias suggests. The change impacts "the ability to tie users that research online and purchase in store," as well as making measuring footfall in stores a "far more opaque" process for clients. A drop in advertiser spending is likely to occur from small or medium-sized advertisers, Kasamias believes, as they are clients "where cost efficiency is paramount and there is a physical footprint, as targeting the right user at the right time will become more difficult." The change has already led to a reduction in "sales pitches from providers of location-data solutions," Havas Media EVP Sargi Mann claimed, with there being more of a need to address the location issue "transparently up front as part of bigger deals" with marketers. Despite the reduced amount of location data available, the amount that is still available to use is more valuable, while the market for location data continues to thrive. "We're still being approached by location data businesses that are telling us they're growing, said Rippll CEO Doug Chisholm. "More importantly, they have more data than they did a year ago." The quality of that data is still a problem, as ad buyers notice it is of a lower quality than data that was previously available. According to Smith, Location Sciences is seeing less location data derived from a smartphone's GPS, "which is the most precise source of mobile location data." Instead, Smith highlights the presence of "lower quality data" sourced from carriers or other Internet protocols. "Often the least accurate sources of mobile location data available" to a marketer in his opinion. The reduction of available data may get worse for marketers, as Apple has urged developers to use " Sign in with Apple " in apps, as an alternative to authentication systems offered by Google and Facebook. While Apple's system will make it harder to track individual users with less data offered to firms, data collection will still be possible for the firms involved.