Ernst & Young estimates in a new publication [pdf] that half of all shareholder proposals in 2011 will deal with environmental and social issues, and support for these proposals is growing. In fact, “83 percent of investors now believe environmental and social factors can have a significant impact on shareholder value over the long term.”

Last year, E & Y finds, approximately one quarter such social investment proposals won 30 percent support –which E & Y calls a “threshold” number, where “many boards take note.”

Perhaps they’d better. Typically, when proposals reach a second threshold — garnering 50 percent support– directors who oppose them start losing their seats.

Things may not yet have reached a tipping point, but these are promising developments. With the enactment of Dodd-Frank in 2010, mandatory say on pay provisions became law; that means fewer executive compensation proposals are on the table, and it’s easier to introduce social issues into the conversation.

There are even some early indications of the trend toward social investment in the 2011 data reported so far on ProxyMonitor.org. (ProxyMonitor – the Manhattan Institute database I relied on in a previous post about why boards say they don’t back human rights proposals — is keeping a “scorecard” of the 2011 proxy season.)

Now the ProxyMonitor data is special, and there might be reason to expect it to tell a unique story. ProxyMonitor documents only proposals made to Fortune 100 companies. Can we reasonably expect Fortune 100 shareholders to set the trend or lead in the area of social investment? On the one hand, investors in the Fortune 100 might tend to be more conservative –and risk averse — than the average shareholder. On the other, these high-visibility public companies with strong brands are likely to attract activist investors and funds with a social agenda. The likely outcome is more proposals, less traction.

Be that as it may, so far, a clear majority of shareholder proposals made to Fortune 100 companies in 2011 target social investment issues.

And there is another encouraging trend here. More and more shareholder proposals ask boards of directors to report on corporate political spending and contributions. The Findings page on ProxyMonitor notes that among Fortune 100 companies, “the share of social policy proposals focusing on political spending has increased 84 percent in 2011 from the three previous years (2008-2010)” [emphasis mine].

A few examples give some sense of where things are heading. Two proposals requiring Valero Energy Corporation to report on its political contributions received 26 and 27 percent support, edging closer to the 30 percent threshold of boardroom visibility. A proposal by AFSCME asked IBM to disclose “direct and indirect spending to influence legislation as well as grassroots lobbying communications to influence legislation”; it received 28.5 percent support in the 2011 vote. It will be hard for the IBM board to ignore or resist this much longer.

All is not sunshine. It’s worth noting that when AFSCME advanced similar proposals with Prudential and Bank of America, both proposals met with zero support. [Update 5/16/11: this is incorrect. Please see this post.] Prudential made the case that the information is already available; Bank of America complained that it would be burdensome and redundant, and, besides, “our company does not engage in grassroots lobbying.”

Make of that statement what you will. It’s clear that forcing disclosure of so-called “indirect” and “grassroots” spending will be an uphill battle, in part because it is difficult to define or track grassroots spending, or distinguish it from legitimate trade association activity.

But the focus now on corporate political spending brings welcome relief. As I suggested in an earlier post, some social investors are trying to do what Congress is unable or too cowardly or too compromised to do: take back some of the ground that was lost or – as I prefer to put it – given away by the courts in Citizens United. The boldest of these proposals, requiring Home Depot not only to disclose its political expenditures, but also to submit those expenditures to a shareholder advisory vote, will come to a vote on June 2nd. Maybe this measure will make it past the threshold.