At least 75 companies receive anonymous, precise location data from apps whose users enable location services. Several of those businesses claim to track up to 200 million mobile devices in the United States - about half those in use last year. The database reviewed by The Times ... reveals people's travels in startling detail, accurate to within a few yards and in some cases updated more than 14,000 times a day. These companies sell, use or analyze the data to cater to advertisers, retail outlets and even hedge funds. It's a hot market, with sales of location-targeted advertising reaching an estimated $21 billion this year. Businesses say their interest is in the patterns, not the identities, that the data reveals. They note that the information apps collect is tied not to someone's name or phone number but to a unique ID. But those with access to the raw data - including employees or clients - could still identify a person without consent. They could follow someone they knew, by pinpointing a phone that regularly spent time at that person's home address. More than 1,000 popular apps contain location-sharing code from such companies. Google's Android system was found to have about 1,200 apps with such code, compared with about 200 on Apple's iOS.