The simple rule of thumb is that the more information, and the more up- to-date it is, the more expensive it will be. Services range from real- time share prices to overnight or hourly updates, plus historical market data and company information.
Some packages offer stock movement alerts and individual analysis, so you don't even need to monitor your portfolio for 24 hours a day to manage it successfully.
All this costs money, of course, but if your portfolio is worth pounds 30,000 or more, having the right information at your fingertips at the right time can help that portfolio grow. In the investment world knowledge is power - and private investors now have direct access to that power.
The Stock Exchange Market Eye service, for example, offers information similar to that which stock market professionals get throughout the day from their Topic screens; both are supplied by the same company, ICV. The service was originally introduced in 1984; since then a range of services has been launched at different prices, offering different levels of information.
Market Eye offers a full range of real-time information including the opening price, the day's highs and lows, sales volume, and bid and ask prices, for up to to pounds 2,000 a year.
At the other end of the scale, Internet users can obtain stock market prices updated hourly, plus access to company data and a low-cost share- dealing service, from ShareLink for as little as pounds 60 a year.
It's a question of finding the service which meets your level of interest. If not actively trading a portfolio, you may not need real-time pricing; if dealing only with FT-SE stocks, it may be pointless to subscribe to a service providing information about options and futures.
However, if you're seeking portfolio management you probably need a service which allows you to focus on your own stocks. Market Eye, for instance, allows you to set up your own pages, with up to 50 shares on a page, and obtain at-a-glance information as to whether you need to start buying or selling. Market Eye enables you to customise pages containing equities, gilts, fixed interest and index options.
With Market Eye, share price information is transmitted via a teletext adapter that sits inside a Windows PC and works with the ICV software. Buying the adapter, or datacard, costs around pounds 450.
For serious investors with a portfolio beyond the UK, Reuters 1000 delivers a wealth of international market data using a teletext feed from CNN International, the satellite television news service.
Information on the service includes share prices in near-real-time from London, major European bourses and Wall Street, foreign exchange dealing rates and even the commodity prices from the Chicago Board of Trade. The teletext adapter and software for your PC costs about $800 (pounds 600), with subscription charges a further $100 a month. And, of course, you will need either satellite or cable TV. For the travelling investor, a version of the kit is available for laptops.
Last month saw the introduction of a service using similar technology - Tenfore's Silver subscription, which competes directly with Market Eye. "When it's your money on the line, you want to know exactly what's happening to it," says Barry Jones, Tenfore's general sales manager. "You want to know its precise value at that moment, not when the bank or broker last looked it up."
Tenfore promises that information for pounds 79 a month and, usefully, allows you to monitor market movements by setting price limits which trigger alarms.
The Tenfore Silver system offers Stock Exchange prices and indices; the semi-professional investor can subscribe to a more sophisticated version with full Forex and money market dealer screens for pounds 300 a month. All levels require a satellite dish and decoder at pounds 550, free if you take out a two-year subscription.
Prestel On-Line's screen-based CitiService Premium, which has been around for a little while longer, gives prices for equities and gilts for around pounds 350 a year. It's a dial-up service, so you need a modem.
Infotrade Portfolio, launched last autumn by Mitsubishi Electric, provides a sophisticated range of services to serious stock market investors, including the ability to deal on screen through ShareLink.
"Our objective is to provide private investors with all the means to analyse and invest on a par with City institutions, cheaply and efficiently," says Peter O'Connell, general manager of Infotrade.
The service requires a PC, modem and CD-Rom drive. The basic software and data frameworks are supplied on CD, with regular updates. Subscriptions cost from pounds 10 a month, with a membership fee of pounds 25. There are also on- line charges for share prices, plus up to 80p for copies of articles from the Financial Times, and, as with other dial-up services, there are local telephone charges.Reuse content