In last Thursday's post, I wrote about support for recommendations which can undermine your credibility with clients and prospects alike. I cited two examples - the "stocks are on sale" metaphor as a reason to buy depressed stocks and the impact of "missing best days" as an argument to stay invested.

So if examples such as these don't help make your case, the logical question is what does? For many clients, the answer is hard, objective evidence from a credible source.

Picture this scenario: A client asks about buying gold stocks or a precious metal because he's read that the international banking system is on the verge of collapse, the dollar will become worthless and gold is going to $5000. If you don't happen to subscribe to this view, how do you answer his question?

You could respond that until last summer gold hadn't done much of anything for years - but now you're simply replacing their opinion (or the opinion of whoever wrote that article) with yours.

Better is to walk clients through a chart showing that while gold is indeed up 40% since last August, it is still below its peak price reached in 1980 - and that just to match that price on an inflation adjusted basis, gold would have to hit almost $2500.

But perhaps the most persuasive argument you can make is to pull out your copy of Jeremy Siegel's "Stocks for the Long Run" and show clients his analysis of the real return of $1 invested in 1802 (as far back as data is available) in a variety of asset classes. By 1997 (the last time this analysis was updated), $1 invested in stocks 200 years ago would be worth over $550,000 (and this is AFTER inflation). That same $1 in bonds would have grown to $803.

And that dollar invested in gold? $1 in gold, once you factor out inflation, actually DECLINED in value to 84 cents. (The Economist reached a similar conclusion in an analysis of long term commodity prices going back to the 1600s published in early 2007 - when converted to real terms, the long term price of commodities shows a steady downhill decline).

Your conclusion? It's possible that gold may be a great investment over the next while - but investors who look to gold over the mid and long term are fighting history.

This argument will not work for very client. Some will have already made their minds up - in those cases, there is no evidence that will alter their view. Others will feel overwhelmed by charts and graphs - so you do have to pick your spots. Be selective in using this kind of information (remember, one or two well chosen charts are almost always better than six or eight) and take the time to explain what the charts mean.

There are lots of credible sources to draw from beyond "Stocks for the Long Run" (which should be mandatory reading for every financial advisor serious about the business), There are publications such as The Wall Street Journal and The Economist (both with websites which advisors can access at no cost) - in research with affluent investors, The Wall Street Journal ranks number one for credibility as a source of information. And if you really want to dig into hard core statistical data, take a look at Ibbotson's "Stocks, Bonds, Bills and Inflation" yearbook.

Here's the bottom line: Solid evidence from credible sources often helps you make your case in ways that words alone won't. Clients are more likely to buy in if questions are answered or recommendations supported with hard data of this kind. A side benefit - by letting clients know that your recommendations and opinions are rooted in rigourous research, you reinforce your credibility and image of authority and expertise.