Sun sign astrologers take this basic twelve-fold division and relate all the current movements of all the planets to each other, using traditional rules to divine meanings for each sign separately. Paradoxically, because the Moon has the fastest apparent movement of all the heavenly bodies, it is often used as the main indicator of daily trends for sun sign astrology forecasts.

Despite its vast popularity with the general public (e.g. in the UK over 60% of adults are said to read their "stars" first on opening a newspaper, a slightly higher proportion in the USA[citation needed]), there is much argument about the validity of sun sign astrology, particularly amongst astrologers of different persuasions. The more traditional the astrologer, the more likely they are to dislike sun sign astrology.[citation needed]

As with all astrology, it is considered pseudoscience or superstition by astronomers and most other scientists.

Although William Lilly in the 17th century was the first newspaper astrologer (in fact some people believe that newspapers began as largely-astrological prediction-sheets), sun sign astrology was not invented until 1930. The astrologer R. H. Naylor was claimed by his newspaper to have predicted the crash of the R101 airship. This led to pressure on Naylor to come up with a simplified system of astrology suitable for a newspaper column. After some experimentation, Naylor decided on sun signs.

Owing to the popularity of horoscope columns in many newspapers and magazines, it is often erroneously believed that sun sign astrology is the whole extent of astrology. Some, perhaps many Horoscopic astrologers view these predictions as highly generalized and of little value.

For example, each person also has a Moon sign, a Mercury sign, a Venus sign, etc. These do not conform to the above dates and change greatly from year to year. Sun sign astrologers are unable to take these and many other variables into account.

The argument for sun sign astrology holds that everyone and everything is subject to general forces. For example, a person may plan to walk to the shop the following day, but when they see the weather (which affects everyone) they may change their mind and drive there instead. In this example, a general influence has overcome a personal one. Sun sign astrology says that such generally applicable factors are also found astrologically.

Sun signs are held to represent certain sub-sections of the population. Research by insurance companies within their own massive databases is reported to have revealed differences between the relative safety on the roads of people born at different times of year.[citation needed] The Sunday Times, September 14, 1997 mentions this research and the remarkable results of a marketing company analysing shopping habits by zodiac sign.

The Swiss mathematician and astrologer Gunter Sachs did some extensive research on massive samples (using nearly a million data sets) and demonstrated striking differences between people of different zodiac signs. These results were reported in newspapers all over the world, for example the Daily Mail, November 6, 1997.